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date: 04 October 2022

Meteorology in Vietnam, Pre-1850free

Meteorology in Vietnam, Pre-1850free

  • Hieu PhungHieu PhungUniversity of Michigan


The emergence of meteorology in Vietnam did not begin in 1898–1899, with the French installation of a central meteorological observatory in Phù Liễn, near Hải Phòng, and a network of meteorological stations across Indochina. Prior to the colonial time, the ethnic Vietnamese, as well as other ethnic groups such as the Cham, Muong, and Tay-Thai, developed their own knowledge of meteorological phenomena that functioned within their farming practices and cultural frameworks. While further research concerning traditional meteorological knowledge of minority groups in Vietnam is needed, substantial evidence allows a preliminary survey on the practices of the ethnic Vietnamese. Between 1000 and the 1850s, the Vietnamese expanded outwards from their original homeland in the lowlands of north and north-central Vietnam. They adopted the written language, thought systems, and technologies of imperial China, which predisposed them to an enduring Chinese-style meteorological ideology. The Vietnamese viewed weather extremes and other natural anomalies not merely as natural processes. Because meteorological phenomena were “Heaven-sent” warnings of cosmological disasters, Vietnamese dynastic rulers, as well as local farmers and rice producers, interpreted these signs as a demand for moral change. Redressing the authorities’ governance, according to their view, helped rehabilitate the equilibrium of the cosmos. Hence, the records of weather events in Vietnamese historical documents do not simply describe the conditions of past weather, but more importantly, the situations in which the cosmos was no longer in balance. One need not assume that premodern meteorology lacked material grounds. In Vietnam, meteorological knowledge and practices were strongly associated with wet rice cultivation. Vietnamese authorities maintained official agencies to produce yearly calendars that traced proper timing for rice crops, while the populace accumulated experience-based knowledge about seasonal rainfall. Intellectuals, too, expanded their interests to include meteorological knowledge because the subject enriched their philosophy of nature, as in the case of Confucian thinker Lê Quý Đôn (1726–1784), or their medical practices, as in the case of physician Lê Hữu Trác (1720–1791). The advances of Southeast Asian paleoclimate reconstruction since the beginning of the 21st century have added new ideas and methodologies to the study of premodern meteorology in Vietnam. A stronger partnership between climate scientists and historians will therefore facilitate more sophisticated investigations into the knowledge and practices that the Vietnamese developed to respond to weather and climate dynamics.


  • History of Climate Science


Forming the south-easternmost point of mainland Southeast Asia, present-day Vietnam lies between the latitudes just below the Tropic of Cancer and around 8.6 degrees North. Overall, the country’s climate is governed by bountiful sunshine and high precipitation with a relatively distinctive north–south contrast. For instance, most of the areas in southern Vietnam enjoy more than 2,000 sunny hours per year while the corresponding statistics of the northern part are between 1,500 and 1,700 hours. Using statistics gathered between the 1960s and 2017, Vietnamese climate scientists have agreed on the identification of seven different climate zones, including the Northwest, the Northeast, the Northern Delta (i.e., the Red River Delta), North-Central Vietnam, South-Central Vietnam, Central Highland, and the South (Nguyễn et al., 2017).

The variations in climate in Vietnam can also be understood in terms of change both in the conditions of climate and in human activities over the course of history. While climate scientists have reconstructed the paleoclimates of the areas now lying in the territory of the Socialist Republic of Vietnam, historians have traced the expansion of the ethnic Vietnamese and their interactions with groups who have become minorities in Vietnam. Although a more inclusive history of Vietnam unquestionably awaits to be written, enough evidence allows a preliminary examination on the Vietnamese understanding of weather and climate that preceded the introduction of French colonial/modern scientific knowledge at the turn of the 20th century.

Since observable, instrumental data for Vietnam do not date earlier than the beginning of the 20th century, dendrochronological studies have offered a great understanding of the conditions of Vietnamese climate. Without question, any examination of meteorology in premodern Vietnam should combine tree-ring based hydroclimate reconstructions with relevant historical sources. In this article, meteorology in Vietnam prior to the 1850s will be examined from these two interconnected approaches. Before reviewing the literature concerning evidence from proxy data, such as tree rings, and the potential connection between this data and information from written archives, the article will sketch a history of how the Vietnamese state and its people perceived weather and climate, as well as how they put meteorology in use, during the period from the 11th to the mid-19th centuries.

Conceptualization of Meteorology in Premodern Vietnam

The Transition to Modern Meteorology

The divergence between the Vietnamese traditional approach and the colonial/modern methods to studying weather and climate in the late 19th and early 20th centuries offers a useful perspective into the conception of premodern meteorology. At first glance, the beginning of meteorology in Vietnam can be easily associated with the introduction of colonial science. However, prior to the French colonial period (1862–1954), as the Vietnamese people and other ethnic groups had settled and farmed the land, they had developed their own thought systems and categories to accumulate knowledge about weather and climate. These systems of knowledge are often described as being premodern or traditional. It is difficult to know about these thought systems because colonial and modern meteorology has risen to dominate almost every lens via which one comes to understand climate-related conditions and processes. Moreover, the study of the Vietnamese transition from traditional systems to the modern one remains overdue. Nobuhiko Endo and Jun Matsumoto, for instance, identify important colonial historical sources for the study of meteorological observations in French Indochina. Yet, their report includes no indications about the traditional Vietnamese practices that remained active until the early 20th century (Endo & Matsumoto, 2019). Providing a rare analysis of the role that French Indochinese meteorology played in the international scientific community, Giuditta Parolini similarly leaves the traditional Vietnamese expertise out of the discussion of meteorological practices in Indochina (Parolini, 2020).

In most accounts concerning the implementation of modern meteorology in Vietnam, the starting point dates to 1898. That year, the Meteorological Service and a series of meteorological stations were established in French Indochina. The colonial government was clear about the missions of such apparatuses. To boost colonial production, especially in the agricultural sector, it needed knowledge about the conditions of climate and weather (Doumer, 1902, p. 53; Lê et al., 1995, pp. 307–311). In the following year, 1899, the Central Meteorological Observatory, modeled after the Shanghai Zikawei Observatory, was built in Phù Liễn, near Hải Phòng. These events were momentous in colonial history because this institutional development allowed colonial power to begin collecting and sharing monthly instrumental records across Indochina (Capus, 1902).

But the colonial staff, equipped with modern meteorological instruments, did not observe the conditions of weather in late 19th- and early-20th-century Vietnam alone. While a detailed examination is needed, discrete evidence from writings produced in the colonial time shows that both the native government and the populace continued preserving their practices of watching and responding to climatic dynamics. Due to the expansion of French imperialism in Southeast Asia, the former territory of the Nguyễn dynasty (the native government of Vietnam, whose headquarters were based in Huế, central Vietnam, 1802–1945) was dissected into three different political entities. After having conceded the territory of all six southern provinces to the French in 1862, the Nguyễn court lost its direct rulership over the northern part in the mid 1880s. Notwithstanding the enforcement of French protectorate, the Nguyễn rule survived in the next few decades. Hence, as the French invested in the examination of the Indochinese weather and climate, the last Vietnamese imperial government continued keeping an eye on the same issue, yet in its own way.

The coexistence of the Vietnamese and the colonial climatic records in 1912–1913, for instance, demonstrates the differences between the two meteorological systems. Analyzing the instrumental records collected for 18 years (1912–1929), colonial scientists E. Bruzon and P. Carton suggested that Indochina had experienced a drier condition in 1913, 1914, 1915, and 1920 (Bruzon & Carton, 1930, p. 163). By contrast, the Nguyễn chroniclers reported on a drought episode in 1912 and damaging typhoons in both 1914 and 1915; both reports were on central Vietnam (Hồ & Cao, 1922, pp. 26/7a, 27/16b–17a). This divergence, however, does not imply either record is more accurate than the other. Dendrochronological reconstructions for Cambodia and southern Vietnam have established that 1912 and 1913 were among the 40 driest years of the 759-year period (1250–2008) (Buckley et al., 2010, p. 4/Supplement). Hence, an appreciation of the differences between the Vietnamese traditional meteorology and the colonial/modern scientific approaches requires us to dive deeper into premodern worldviews and practices.

Meteorology in Premodern Terms

Several studies have touched upon the premodern Vietnamese conceptions of meteorology. In all of them, the notion of “sky” lies at the center of the discussion. The term “Sky” (Chinese: ‎/tian; Sino-Vietnamese: thiên; demotic Vietnamese: trời) was highly polysemous in both Chinese and Vietnamese cultures, and analyses of historical climate records in China have also highlighted this concept (Fei, 2018; Pei & Forêt, 2018). It is often translated into English in several ways, including the Sky, Heaven, the Celestial Sky, the Heavenly Sky, or even Nature. In historical Vietnam, “sky” could have referred to the physical space above the earth and the human world. It could also have meant the name of the highest god (or divine force) or the celestial space in which this god resided. In reference to the present discussion, the Sky was not only the realm of meteorological episodes (such as drought or strong wind) and astronomical phenomena (like eclipses or comets) but also one highly associated with a wide range of events on earth, including earthquakes, locusts, or many phenological events.

In the early 1940s, Nguyễn Văn Huyên (1908–1975), one of the few Vietnamese intellectuals who held the Scientific Member position at the French School of the Far East (EFEO) in 1938–1945, delivered a two-part presentation on the Vietnamese custom of drought coping mechanisms (Nguyễn, 1996, pp. 419–457). He argued that the Vietnamese did not merely rely on irrigation work, a strategy strongly supported by colonial/modern science, but also invested in the search for divine aids, including those from the Sky god. In response to severe drought events, the Vietnamese kings would make offerings and pray to various gods. They would also issue tax exemptions and give great amnesty in the kingdom. Most importantly, they would present self-reproach statements in front of the Sky god, who was believed to create the occurrence of drought as a portentous sign. Nguyễn Văn Huyên attributed all these practices to the fact that the Vietnamese state had adopted the Chinese model of governing. In this model, the Mandate of the Heavenly Sky was conferred on a chosen ruler on the ground of his own moral power (‎; đức). When something went wrong with this moral power, the Heavenly Sky would therefore send out warnings in the form of disasters such as drought. Hence, all previously mentioned practices during the occurrence of drought aimed at demonstrating to the Heavenly Sky that the king was making attempts to rectify the omission of his moral duty (Nguyễn, 1996, pp. 570–571). As a trained ethnographer, Nguyễn Văn Huyên also noted the ample rain rituals and festivals observed by the commoners at various local places. Thus, meteorology in traditional Vietnam was inseparable from spiritual and religious practices.

Nguyễn Văn Huyên’s concerns about the meaning of drought in traditional Vietnamese culture were, intentionally or not, part of the attempt to rescue premodern meteorological knowledge from a colonial category of superstition. In an extensive conversation with the colonial literature, Philippe Langlet and Thanh Tâm Quách (1995) revisit high-profile geographer Pierre Gourou’s (1900–1999) remark, which casted grave doubts on the Vietnamese documents of past natural disasters. In arguing that the Red River Delta in northern Vietnam did not historically suffer from water scarcity, Gourou discredited the information about weather extremes and natural anomalies in the Vietnamese dynastic chronicles. The chronicles were, according to him, “at once stilted and naive in which facts are presented without order and without critical examination” (Gourou, 1936, p. 69, 1955, p. 73). Since the chronicles often did not mention the impacts of drought on the crops, Gourou believed that what were reported as drought episodes in these chronicles could not serve as solid evidence for the past conditions of the Vietnamese weather. Langlet and Quách do not entirely reject Gourou’s points. However, like Nguyễn Văn Huyên, they concur that the Vietnamese chronicles did not record natural anomalies “out of naivety” because some records from the chronicles provided brief information about damage level. Such descriptions as a hailstone that could be as large as “a melon” or “a horse’s head” might appear unrealistic. But the evidence from the 20th century does show that Vietnam experienced hailstorms with hail sizes that grew up to about 7 inches (Langlet & Quach, 1995, p. 254; Lê, 1990, p. 72). Overall, Langlet and Quách view that many natural disasters were recorded in Vietnamese chronicles more because of their political implications in the “old political historiography” and less because of the damage level they caused (Langlet & Quach, 1995, p. 256).

Though providing some useful understandings, these pioneering discussions have mostly casted the weather-lore in premodern Vietnam as being stagnant for centuries. The change, if noted, was mainly attributed to the shifts in state ideology. For instance, by pointing to the important influence of animism and Buddhist ideas, especially in the period prior to 1400, Nguyễn Văn Huyên, Philippe Langlet, and Thanh Tâm Quách all imply that, after 1400, the bedrock for the premodern Vietnamese understandings of various weather events was traditional Chinese political theory, or more specifically, Confucianism. Its simplicity aside, this generalization limits itself to only one or two aspects of premodern Vietnamese meteorology. Against this context, several topics should be the focus of the future research on the conceptions of meteorology in premodern Vietnam.

First, there is a need for a deeper investigation into the utility of Chinese-style political philosophy as a theoretical framework for premodern Vietnamese meteorology. Mark Elvin’s creative analysis of what he terms “moral meteorology” in late imperial China is highly relevant (Elvin, 1998). At the core of moral meteorology was the “belief in human responsibility for the weather, mediated through the responses of Heaven to humankind’s moral and immoral behavior” (Elvin, 1998, p. 214) In essence, this concept is in line with what Nguyễn Văn Huyên, Philippe Langlet and Thanh Tâm Quách refer to as the Chinese-style political theory that the Vietnamese adopted in their meteorological observations. However, Elvin advocates for an important point. Moral meteorology was not the single approach to weather and climate in Chinese-style political culture. Hence, the Chinese emperors did not automatically apply this moral approach to explain climatic dynamics. In fact, the moral meteorology in Qing China from the 17th to the mid-19th century demonstrates the practice of some quasi-scientific ideas. These ideas are mostly manifested in the Qing emperors’ efforts to validate the outcomes of human responses to Heaven’s warnings. For instance, the cause of a drought episode at a specific area would be explained not in universal terms that pointed to the emperor’s moral capacities. Instead, the scale of moral meteorology mattered: the responsibility lay on the bad behaviors of the corresponding local people (Elvin, 1998, pp. 225–228). Elvin’s argument is suggestive because it raises the question about the historical contexts and the mechanisms in which moral meteorology was in effect in premodern Vietnam.

Second, the Vietnamese premodern methods to forecast weather deserve more scholarly attention. To do so requires a greater appreciation of the affinity between meteorology and other traditional bodies of knowledge such as astronomy, physical geography, agronomy, medicine, as well as the arts of prognostication (Kory, 2020). The interconnection among these traditional disciplines implies that astronomical and meteorological events could have had inherent relations. Hence, astronomical events could have served as “data” for weather forecasts. This interconnection also allowed forecasting techniques from one science (like astronomy) to be applied to examine the subjects of the other sciences (such as meteorology). Calendar making, an astrometeorological practice that the Vietnamese adopted from traditional China, is probably the best example. Many different timelines were integrated in a traditional Vietnamese calendar, as they were in the Chinese counterpart. Not only were the motions of the Sun and the Moon tracked but seasonal changes were also observed. Highly relevant to weather forecast techniques is the presence of the twenty-four fortnightly periods (節氣‎; tiết khí). In this timeline, a year is divided into 24 periods, each “corresponds to 15o motion of the sun in longitude on the ecliptic” (Needham & Wang, 1959, p. 405). However, the names of these periods demonstrate a strong agrometeorological orientation. For instance, the names of the sixth to ninth periods, which fall in the timespan between late April to early June, are subsequently “Grain Rain” (穀雨‎; cốc vũ), “Beginning of Summer” (立夏‎; lập hạ), “Lesser Fullness (of Grain)” (小滿‎; tiểu mãn), and “Grain in Ear” (芒種‎; mang chủng) (Hoàng, 1998, p. 1041; Needham & Wang, 1959, p. 405; Nguyễn & Bùi, 2019, p. 88). Thus, the knowledge about and techniques to trace the movements of celestial bodies, as well as the rhythms of seasonal changes, were used to predict the proper weather patterns needed for agricultural activities.

Finally, the matter of spatiotemporal adjustments demands more research. Throughout its history, Vietnam has always been occupied by a variety of ethnic groups. The officially recognized number has been 54 ethnicities since 1978. While the written history often traces a history mostly centered around the ethnic Viet people, the knowledge accumulated by this ethnic group alone does not represent the full picture of meteorology in Vietnam. A telling example is the contribution of the ethnic Cham. The Cham settled along the coast of central Vietnam and in some parts of the south prior to 1800. They adopted calendar-making techniques from Indian, Chinese, and Islamic cultures and developed their own calendric systems to forecast the suitable time for farming (Sakaya, 2016, pp. 136–150). The interinfluences between the ethnic Viet people and other ethnic groups in producing meteorological knowledge and practices are also in dire need for future research. For instance, the Muong people, an ethnic minority sharing deep historical roots with the Viet people, long developed a calendar system that extensively used the motion of the Moon and the Pleiades, or the Đoi constellation in their language (Phạm & Lê, 2021, pp. 121–123). Likewise, many ethnic Viet people in northern Vietnam traditionally observed the motions of the same constellation, which they called the Tua Rua or the Mạ (lit., “pre-germinated rice seedlings”), to identify the beginning of rice crops (Bùi, 1999, pp. 42–43, 92–93, 100, 120).

In short, prior to the domination of colonial and modern meteorology, the Vietnamese developed their own approaches to explore and respond to climate- and weather-related processes. To them, natural phenomena such as rainfall, earthquakes, thunder, and drought carried cultural implications because they were often deemed portentous. A weather extreme could represent an act of a divine force or a sign for certain emerging disturbance in the relationship between human beings and the cosmological-natural force. In addition, the concerns about weather and climate in traditional Vietnam were basically agrometeorological. Hence, to interpret a premodern report on a drought episode or a flood requires a sufficient understanding of the Vietnamese agricultural activities, and specifically, their rice cultivation.

Premodern Meteorology in Practice

Because meteorology, as well as other kinds of scientific knowledge, has been often overlooked in the study of premodern Vietnam, many aspects of Vietnamese meteorological practices remain difficult to access. To provide some suggestions on this overdue topic, this section first demonstrates that meteorology was more of a state affair and less of a private enterprise in premodern Vietnam. For centuries, Vietnamese rulers maintained a state bureau in charge of working with weather issues. Second, while meteorology in Vietnam was not separate from cosmology and religion until the 20th century, the Vietnamese used weather-lore to guide their agricultural activities as well as to engage with other sciences.

Meteorology as a State Affair

Like their Chinese counterparts, Vietnamese rulers installed specialized agencies to keep track of many natural processes, including weather events. The most important bureau was the Directorate of Astronomy. This office was first established in the second half of the 15th century, even though its antecedents had been operating since several centuries earlier. Between the mid-15th century and the early 20th, the Directorate of Astronomy was known by different names: it was the “Bureau of Sky-Related Management” (司天監‎; Tư Thiên giám) from the 15th to the 18th century and the “Directorate of Obedience-to-the-Sky” (欽天監‎; Khâm Thiên giám) in the 19th and early 20th centuries. Both agencies originated in the traditional Chinese administrative system; the former was especially active during the Song dynasty (960–1276) while the latter in the Ming (1368–1644) and Qing (1644–1912) periods. If the premodern weather-lore involved the knowledge of many closely-related fields such as astronomy and geography, the work of the Directorate of Astronomy was also multidisciplinary. Confucian scholar Phan Huy Chú’s (1782–1840) observations about the changes of the Vietnamese bureaucratic structure in the second half of the 18th century provide a glimpse into the mission of this office. The Directorate of Astronomy served “to extrapolate the celestial degrees, to make calendars, to ensure the timely occurrence of all things, and so on” (Phan, 1821, p. 13/12b). In particular, “when finding that there are disastrous anomalies and omens,” Phan noted, “the officials of this bureau must listen to all different hypotheses and make full reports about them [to the royal court]” (Phan, 1821, p. 15/65a). Hence, the Directorate of Astronomy was commissioned both to forecast sky-related events that were deemed regular (as in the calendar making) and to keep records of and interpret irregular episodes like drought or excessive rainfall.

The Vietnamese rulers began keeping records of weather-related events at least from the early 11th century. This was the time when the first long-term Vietnamese dynasty, the Lý (1010–1225), was established. Some state-sponsored activities in astronomical observations and calendar making date to this time (Lê et al., 1697, p. Bản kỷ 2/20a; Volkov, 2013, p. 117). Reports on meteorological events, such as drought (year 1071), rain with hail (year 1078), or river floods leading to harvest failure (year 1164), also appear frequently in the state chronicles. Because the Lý dynasty, and its successors, the Trần (1225–1389), ruled the Vietnamese kingdom from their headquarters in the capital of Thăng Long (present-day Hanoi), most of the recorded meteorological events were observed from there and areas surrounding Hanoi.

More solid evidence for the antecedents of the Directorate of Astronomy emerges in historical documents dating from the 13th century. Vietnamese dynastic chronicles subsequently mentioned three different offices, the work of which were similar to that of the Directorate of Astronomy. The first bureau was the Office of the Grand Supplicant (太祝司‎; Thái Chúc ty). During the Trần dynasty, it held an examination to recruit new staff in 1261, indicating that it must have been established even in an earlier time (Lê et al., 1697, p. Bản kỷ 5/26a). No Chinese governmental agencies ever bore this precise title, but the Grand Supplicant was a specialist in royal rituals, a job that certainly required the knowledge of astronomy and calendar making. The other two bureaus were the Astrological Service (太史局‎; Thái Sử cục) and the Astrological Commission (太史院‎; Thái Sử viện). The Office of the Grand Supplicant was replaced with the Astrological Service at some point between 1261 and 1339 before it was retitled as the Astrological Commission in the 1450s (Phung, 2017, p. 168). Although weather forecast was not likely to be the central task of the staff at the Astrological Service/Commission, the Vietnamese rulers’ great investment in astronomy and calendar making was only one side of the coin. The other side involves interpreting natural anomalies, including phenomena like drought and excessive rainfall, and recommending the right responses (often in the form of rituals) to these anomalies.

The Bureau of Sky-Related Management, or the Lê Directorate of Astronomy, was formed at some point towards the end of the 15th century, and it existed until the falling of the Lê dynasty in the late 18th century. During this period, Vietnamese rulers developed stronger networks that helped transmit weather-related information between the central government and the local people. For instance, the royal court distributed the yearly official calendar to the members of the royal family and multiple state representatives who were stationed at local areas. The beginning of this practice in Vietnam remains unknown, but the state jurisdictional corpora on administrative matters in the 18th and 19th centuries carefully noted of it (Anonymous, c. 1750s, pp. 3/29b–30a; Grand Secretariat of the Nguyễn Dynasty, 1851, pp. 80/1a–3a). Further, the Provincial Surveillance Commission (憲司‎; Hiến ty), one of the three key commissions appointed by the central state to oversee local affairs, was assigned to investigate and report on all disturbing local issues. These issues included weather-related disasters such as droughts and floods (Lê et al., 1697, pp. Bản kỷ 19/37b–38a; Phan, 1821, pp. 14/41b–42a).

A new development in the 17th and 18th centuries is the existence of two different Vietnamese regimes; both established their own agencies to watch sky-related phenomena. The Lê kings continued to rule the northern part of Vietnam, although the Trịnh lords were the de facto power. To the south, the Nguyễn lords formed a rival power against the Lê-Trịnh state. At the peak of its power, the Nguyễn ruled over a territory that stretched from present-day Quảng Bình province to the northern bank of the Tiền Giang River (one of the branches of the Mekong River in Vietnam). As the Lê-Trịnh administration relied on the Directorate of Astronomy and the Provincial Surveillance Commission, the Nguyễn lords maintained the Office of Omen Watching (占候司‎; Chiêm Hậu ty), or an agency that prognosticated atmospheric conditions (Trương et al., 1961, p. 89 [6/4a]). During the 17th and 18th centuries, the Directorate of Astronomy and the Provincial Surveillance Commission of the Lê-Trịnh state and the Office of Omen Watching of the Nguyễn administration performed their work in two different areas of Vietnam, producing separate reports on astronomical and meteorological events.

Little is known about the office and its personnel that reported on weather events and other sky-related phenomena at the turn of the 19th century due to many contemporary political upheavals. Soon after coming to power, the first emperor of the Nguyễn dynasty established a new office to oversee sky-related matters. This office was the Directorate of Obedience-to-the-Sky, or the Directorate of Astronomy of the 19th century. As the last imperial power in Vietnam, the Nguyễn dynasty left behind more source materials about their meteorological practices. Some cursory observations show that the Nguyễn Directorate of Astronomy did not break with many traditional tasks, including observations of celestial bodies, calendar making, and divination of natural anomalies (Dyt, 2015). However, there are several meaningful changes. First, since the Nguyễn’s territory was much larger than that of previous Vietnamese rulers, to unify meteorological knowledge between the central government and the locals became more complicated. From the beginning, the Nguyễn court introduced the use of daily weather report forms. No such forms exist to date. The Nguyễn chroniclers described a weather report form as a horizontal diagram on which a reporter could mark a date as being sunny or rainy. Since 1814, local officials would prepare these weather reports and return them to the central court every month (Trương et al., 1961, p. 906 [48/21a]).

Second, the Nguyễn authorities engaged in experimenting new meteorological instruments such as barometers (風雨尺‎; phong vũ xích; lit., “wind-and-rain meter”) and thermometers (寒暑尺‎; hàn thử xích; lit., “cold-and-heat meter”). They must have obtained these devices from Qing China and/or from Western missionaries. At first, in 1826, the central court sent barometers and thermometers to select jurisdictions like Gia Định (Saigon) and Bắc Thành (Hanoi). These were the most important political centers besides the royal capital in Huế. Three other provinces, two northernmost (Tuyên Quang and Lạng Sơn) and one southernmost (Hà Tiên), also received these new instruments. Five years later, during 1831–1832, the Nguyễn administration provided thermometers to all the other provinces, which had not been selected in 1826 (Phan et al., 1961, pp. 1931–32 [40/26a–27a], 2438 [73/3b], 2572 [82/2a]). The utility of barometers and thermometers did not mean a replacement of older technologies. These new instruments helped extend the current meteorological practices because they provided the information of atmospheric pressure and temperature. By contrast, the more common meteorological practices in Vietnam mostly entailed precipitation. For instance, when recounting a drought episode in Huế in the sixth lunar month in 1858, the Nguyễn chroniclers commented that the water collected in the brass basin had not reached even 1 phân (about 4 mm) the day before. However, as it was rainy, there was about 2 phân of water in the brass basin. As they checked dry ground, they found that the water soaked 6 phân below the soil surface (Nguyễn et al., 1961, p. 6088 [18/27b]). Hence, the Nguyễn rulers were probably familiar with some sort of rain gauge and other non-Western techniques to measure precipitation.

Interdisciplinarity of Weather-Lore

If Vietnamese authorities took meteorology as an important affair of the state, Vietnamese intellectuals applied weather-lore in multiple ways. One of these applications was the use of meteorological knowledge to engage with natural sciences. Another, probably more common, application was the identification of local disparities. Like in China, Vietnamese writers produced historical gazetteers that collected a wide range of information about a specific local area. The production of these gazetteers formed a specialized writing genre, often rendered in English as “local gazetteers” (輿地志‎; dư địa chí). The modern equivalent of this genre would be historical geography. Although the volume of Vietnamese local gazetteers is often much modest than their Chinese counterparts, certain information in these texts indicates that the compilers took climate as one of the local identifiers. An important feature of each local gazetteer is that it presents information in categories. Common categories include borders and territory, mountains and rivers, historic attractions, historical people, and local customs.

In Vietnam, it was not until the turn of the 19th century that climate emerged as a distinct category in gazetteers. However, information about local climate had long been categorized as part of the knowledge about local customs. Early sources often include meager, yet suggestive, evidence. For instance, in a description of the local customs (風俗‎; phong tục) of the Vietnamese kingdom in the 13th and 14th centuries, a contemporary writer described that, because the local area is often as hot as the midsummer weather (暑熱‎; thử nhiệt), its people love bathing in rivers and they are skillful at sailing and swimming (Lê, c. 1300s, p. 1/17b). A 16th-century writer similarly used climatic information to describe a southern frontier called the Ô prefecture. In this case, the Ô prefecture covers much of the land in central Vietnam. The beginning of the section “Local Customs” reads:

Regarding the local climate (天時‎; thiên thời), it is often hot in spring and summer and rainy in autumn and winter. In terms of the local specialties, the summer harvest is more productive than the autumn one. Speaking of the weather (氣運‎; khí vận; lit., “circulation of the vital force”), it is often getting humid and hot than getting cold. Speaking of the topography (地形‎; địa hình; lit., “form of the land”), there are many high mountains and [the land] opens to the sea. The typhonic sky (颶母‎; cù mẫu) frequently occurs during the midsummer, and the sky is not often clear on the night of the mid-autumn full Moon. (…) Sea tides occur twice every day.

(Dương, 1555, p. 38b)

This 16th-century account highlights several important climatic themes, on which later writings would continue elaborating. These themes include temperature, precipitation, the characteristics of wind, the dynamic appearances of sky, the occurrence of sea tides, as well as seasonal crops. Two telling examples from the 18th- and 19th-century writings are the descriptions in a subsection entitled “Climate” (天氣‎; thiên khí; lit., “the vital force of the sky”) in Bùi Dương Lịch’s (1757–1828) Records of Nghệ An and an appendix entitled “Observations of Climate” (占天氣候‎; chiêm thiên khí hậu) in Trịnh Hoài Đức’s (1765–1825) Comprehensive Gazetteer of Gia Định (Bùi, c. 1800s, pp. 2b–5b; Trịnh, c. 1800s, pp. 1/3b–5a).

By the mid-19th century, as the Nguyễn court sponsored a massive project to compile comprehensive gazetteers of all 31 provinces in the kingdom, local climates became an autonomous variable that helped identify local differences. In this project, “climate” became a unique category separate from “local customs” (The Institute of History of the Nguyễn Dynasty, c. 1800s). A quick survey of these accounts confirms the recurring themes from the climatic accounts in the previous local gazetteers. To demonstrate the disparities in provincial conditions, the compilers of the Nguyễn gazetteers referred to local climates in three aspects: characteristics of seasons, agricultural calendar, and features unique to certain provinces such as information about wind, storm, and sea tides in coastal areas. For instance, Hanoi and its neighboring provinces were characterized by the presence of four distinct seasons. Yet, the local topography made crop timing different from one province to another. In Sơn Tây, a province west of Hanoi, the planting work was not completed until the end of the first lunar month in a summer rice crop and the end of the eighth lunar month in an autumn crop. The gazetteer compilers noted, “this is a bit later than those southeastern provinces” (The Institute of History of the Nguyễn Dynasty, c. 1800s, p. 31/13b). While Sơn Tây was at the transitional zone between the upper and lower reaches of the Red River, the southeast provinces including Hưng Yên, Nam Định, and Ninh Bình were all in the lower streams. The summer crop in Nam Định, for instance, began in the twelfth lunar month of the previous year, and its autumn crop in the sixth lunar month.

Meteorology was not only a tool to identify local disparities but also a field via which Vietnamese literati came to engage with early modern sciences. The two examples discussed here are contemporaneous; both contributed to the 18th-century discourses on one of the most important notions in traditional Chinese (and Vietnamese) sciences, “the vital force” or qi (‎; Vietnamese: khí; other translations: pneuma, vapor, vital energy, materia vitalis). Lê Quý Đôn’s (1726–1784) Catalogued Discourses of the Library (1773), which is in the form of an encyclopedia, includes nearly 1,000 entries which were divided into nine different categories. The key theme of the entries in the first category is the nature of the vital force and its paired concept, “principle” (‎; ). These are fundamental and complicated concepts originating from the Confucian movements in medieval China (Lin, 2020). However, relevant to the present discussion on meteorology is the subsistence and dynamics of the vital force. Lê Quý Đôn forcefully defended that the vital force is not conceptual; although it is unseen, it is what “fills up the sky and earth” (Lê, 1773, p. 1/1a). To demonstrate the existence of the vital force, he cited meteorological phenomena. For instance, Lê explained the nature of wind, rainfall, and fog in terms of the effect of the vital force. Here, the vital force is not very different from a mixture of gasses.

The dry vital force generates wind; as wind disperses, the sky becomes clear. The moist vital force forms clouds; as clouds accumulate, it is rainy. [These processes are all governed by the creation of] the vital force [that has] neutralizing and streamlining effects. When the dry and the moist vital forces collide with one another, fog is the result. A large amount of accumulated fog will generate toxic atmosphere (‎; chướng); this is because of the vital force that becomes malevolent and stagnant.

(Lê, 1773, p. 1/3a)

The second example is from a medical text written by Confucian-physician Lê Hữu Trác (1720–1791), the Reflective Compendium on Breathing Exercise (1776). The core philosophy upon which Lê Hữu Trác’s discussions were based originated from the famous Chinese classic Book of Change (易經‎). Both the knowledge embedded in the Book of Change and Vietnamese traditional medicine are highly complicated subject matters. For the purpose of the present discussion, the main reason why a physician like Lê Hữu Trác invested himself in meteorology is the fact that diseases were highly associated with the conditions of the environment, especially the rising of “malevolent wind and baleful vital force” (惡風惡氣‎; ác phong ác khí) (Lê, 1776, p. 4b). Hence, Lê Hữu Trác devoted a full section of his text to discussing the devices and techniques that one could use to diagnose the conditions of clouds and wind, as well as the changing look of the sky. While Lê Quý Đôn traced the nature of the vital force by using meteorological phenomena, Lê Hữu Trác focused on the practicality of weather-lore. His text was even attached with several graphics of devices that helped the observing of the sky and wind directions (Lê, 1776, pp. 8a–9a).

Between 1000 and the 1850s, Vietnamese authorities and intellectuals were deeply invested in developing institutions that enabled the growth of meteorological knowledge. They also applied meteorology in other fields of study such as agronomy and medicine. These serious engagements with meteorology help explain the existence of relatively rich records on weather events and other anomalies in premodern Vietnam.

Writing the Premodern History of Weather and Climate

The Medieval Warm Period in Vietnam

The article written by Victor Lieberman and Brendan Buckley (2012), which is a pioneering collaborative project between a historian and a climate scientist, offers an excellent model for what needs to be done in the study of premodern Vietnamese meteorology. By reviewing the main factors (solar activity, volcanism, and ocean currents) that affected the global atmosphere in the period prior to 1850, the authors contend that paleoclimatic data from Southeast Asia presents a matching pattern. Specifically, the evidence illustrates that the earth became warmer between the 10th and the late 13th centuries. This period is known as the Medieval Warm Period or the Medieval Climate Anomaly. By contrast, multiple cooling phases occurred between 1280 and 1825, collectively referred to as the Little Ice Age. More importantly, Lieberman and Buckley highlight two key features in the climate history of Southeast Asia. First, the position of the Inter-tropical Convergence Zone was likely to shift southward during the transition to the Little Ice Age. The result of this shift was that more dramatic effects of the climate should have occurred in such an area as Cambodia where, from the 9th to the 15th centuries, the kingdom of Angkor was located. Second, paralleling the climatic dynamism to sociopolitical changes in the region, Lieberman and Buckley argue that changes in the climate had a greater impact on many societies in mainland Southeast Asia during the Medieval Climate Anomaly. However, the impact of climate reduced after 1450. The waning scale of monsoon fluctuations is one reason, and another is the fact that the social and political transformations in the region made its peoples less dependent on the exclusive governing of climate.

Lieberman and Buckley’s article is a success and the first of its kind in consolidating two important theses in Southeast Asian climate history: the impact of the Medieval Climate Anomaly and the relationship between the 18th-century megadrought and the sociopolitical upheavals in mainland Southeast Asia. A decade before his collaboration with Brendan Buckley, Victor Lieberman speculated on the impact of the Medieval Climate Anomaly in mainland Southeast Asian societies in his monumental monograph Strange Parallels (2003). Regarding the case of Vietnam, he asked a seminal question: if dry areas in Pagan (Myanmar) and Angkor (Cambodia) benefited from stronger monsoons, how did the same condition affect the Red River Delta? To answer this, he suggested a closer examination of the large-scale dike systems that Vietnamese authorities began to build in the mid-13th century (Lieberman, 2003, p. 363). Li Tana, a historian of Vietnam, has attempted to elaborate on Lieberman’s hypothesis. She concurs that the Trần authorities’ massive dike project that flanked the Red River network was encouraged by an episode of warming climate (Li, 2016b, pp. 360–361). This climatic condition also led to a demographic surge, especially on the eastern Red River delta, which triggered a wave of migration into the western delta (Li, 2014, 2015, 2016a, 2016b).

Two curious studies prior to Lieberman and Buckley’s work deserve some attention. These studies take different approaches, one inherently historical and another palynological, but their findings are useful when considering the question of the Medieval Climate Anomaly. In 1983, Nguyễn Xuân Tửu—a Vietnamese expert in hydraulic engineering—offered a brief survey on the shifting temperature in historical Vietnam (Nguyễn, 1983). His generalization did point to a significant climatic transition during the 15th century. Specifically, the 13th and 14th centuries became warmer, followed by a cooler condition, which featured colder winters in northern Vietnam during most of the 15th century. From the 15th to the 19th centuries, the fluctuations in temperature seem to have become more dramatic as the shift between warmer and colder winters occurred more frequently. Hence, Nguyễn Xuân Tửu’s observations further support the idea that the transition to the Little Ice Age began in the 15th century. However, even though Nguyễn implied that the conditions of the 20th-century climate serve as a means of comparison, he did not provide any qualification for his evidence, most of which comes from Vietnamese chronicles.

While a few studies on pollen sediments in the Red River Delta have focused on the last deglaciation, a geological period that ended some 6,000 years ago, one palynological study on the southeastern coast of northern Vietnam has examined the period from 466 to 1876 (Li et al., 2006). In it, the climate condition of our present time (approximately from 1876 to 2006) is defined as being warm and dry. Accordingly, the period from 466 to 1386 experienced similar conditions. After 1386, a cooler and wetter climate characterized the centuries to 1876. Overall, these findings confirm the Medieval Warm Period thesis, but its suggestion that the climate became drier after 1176 challenges Lieberman and Buckley’s argument on the stronger impact of monsoons in Vietnam at that time. The topography of the area from which evidence for this study was collected plays an important role. The southeastern Red River Delta was often referred to as a wet zone in historical sources. If it experienced a somewhat drier climate after 1176, the condition of local soil might have become more favorable for cultivation.

Climate Dynamics in Vietnam During the “Little Ice Age”

Dendrochronological data from Southeast Asia are much more robust for periods within the timespan of the so-called Little Ice Age. Hence, a greater number of studies from climate science have offered evidence to test the thesis on the 18th-century megadroughts. The most vigorous data comes from the Monsoon Asia Drought Atlas (MADA) (Cook et al., 2010; Wahl & Morrill, 2010). The MADA is “a seasonally resolved gridded spatial reconstruction of Asian monsoon drought and pluvials over the past millennium, derived from a network of tree-ring chronologies” (Cook et al., 2010, p. 486). This atlas has three important technical features: First, it includes tree rings from more than 300 sites, which allows for a reconstruction of the period starting from 1300. Second, it represents data on a 2.5° latitude/longitude grid. And third, it aims to “reconstruct the seasonalized Palmer Drought Severity Index (PDSI) for the summer (June–July–August) monsoon season” (Cook et al., 2010, p. 486). In this way, the MADA helps identify “regional patterns of drought and wetness,” that is, reconstructions of the spatiotemporal conditions of the past climate (Cook et al., 2010, p. 487). Here, the data for a decade-long drought episode in 18th-century mainland Southeast Asia is robust (See also: Sano et al., 2008). Inspired by Victor Lieberman’s characterization of the sociopolitical upheavals in the same period, the team of MADA scientists has used the title of his monograph to refer to the megadrought in the region, lasting from 1756 to 1768, as the “Strange Parallel” drought (See also: Lieberman & Buckley, 2012, p. 1091).

While the MADA is useful in identifying the climatic patterns of relatively large regions, study into the past climate of Vietnam requires higher resolution data. Brendan Buckley has been the most active scientist working in multiple collaborative projects on the conditions of the Vietnamese paleoclimate (Buckley et al., 2014, 2017; Sano et al., 2008; Stevens et al., 2018). A study he led in 2014 offered the first attempt to correlate evidence about weather extremes from Vietnamese chronicles with other proxies, especially tree rings (Buckley et al., 2014). This study also provided a good insight into the differences of historical evidence about the conditions of climate in northern and central Vietnam, as well as the valuable observations made by Western missionaries in the 17th and 18th centuries. However, while the historical evidence strongly supports the 18th-century megadrought, it poorly resonates with the information from the MADA for the 17th century. Using historical evidence from both native and missionary sources, Buckley and his colleagues suggest that, although the MADA shows great variability in the climate across Southeast Asia during this period, the problem probably lies in the imperfect nature of historical documents (Buckley et al., 2014, p. 12). Efforts to marry historical information with reconstructions of paleoclimate in Vietnam, therefore, remain open for future projects.

Integrated Analysis Between History and Paleoclimate Science

Climate scientists have long attempted to perform a seasonal hydroclimate reconstruction of Vietnam. Sano et al. (2008), for instance, provide a dendrochronological time series that well illustrates the 18th-century megadrought over northern Vietnam. However, their research results present the March–May (MAM) PDSI, which is not the time most responsible for yearly accumulation of rain. To merge historical evidence with other proxies, the reconstructed variable matters. This is because the growth of meteorological knowledge in premodern Vietnam had strong implications in agrometeorology.

In other words, much historical evidence about climate and weather from premodern Vietnam emphasizes the kind of climatic impact on the rice crops. In northern Vietnam, the practice of the summer rice became relatively productive only after the mid-15th century (Phung, 2017, pp. 142–154). Hence, the impacts of drought on the rice economy should have been different for the periods before and after the 1450s. A meticulous historical reconstruction by Yumio Sakurai (2001) finds that about 79.1% of 64 recorded drought episodes that occurred between 1422 and 1786 fell in the period between the first and the sixth lunar months, that is, between late January–early February and July–August. According to Sakurai, most of the recorded drought events in Vietnamese chronicles implied that there was damage to the summer rice crop. Furthermore, Sakurai argues that the harder impact of drought in a certain region should have been linked to the period when that region experienced an increase in farming of summer rice. This conclusion is highly compelling. However, Sakurai provides little to no explanation about the methodology he uses in analyzing the imperfect nature of his historical sources.

The question of seasonal hydroclimate conditions in premodern Vietnam, therefore, continues to pose difficulties for climate scientists, as well as historians. Hansen et al. (2017) coordinate three separate sets of dendrochronological reconstructions to analyze drought episodes that occurred in different seasons. They find that the megadroughts in the 18th century were present across all seasons. By contrast, the mid-19th century experienced the worst autumn drought but only moderate dry time in spring and summer. This data analysis, however, does not cover a time span that goes back further than the mid-17th century.

While findings in climate science will continue to rely heavily on the attainment of new data and application of improved methodologies, the answers to many historical questions about meteorology in premodern Vietnam depend on more systematic and comprehensive research of the relevant written information. This enterprise especially requires interpreting meteorological information in premodern texts within the historical culture from which it was produced and utilized. Such research has been often overlooked, in part because most premodern Vietnamese historical documents were written in old languages that are no longer in use in Vietnam, specifically classical Chinese and demotic Vietnamese Nôm script. Moreover, these kinds of information entail premodern systems of thought and classification, which significantly differ from modern, scientific-based conceptions of climate, and which have yet to receive the needed appreciation.

The historical analysis, therefore, needs to focus first on the Vietnamese chronicles. These texts, written in classical Chinese, offer chronological records of weather-related events from the 11th to the late 19th centuries. Several studies have used these sources, but there exists no systematic analysis of them (Buckley et al., 2014; Dyt, 2016; Li, 2014; Phung, 2017; Sakurai, 2001). One collection of historical evidence about Vietnamese meteorology and hydrology published in 1995 is a significant contribution (Lê et al., 1995). However, this publication does not provide the original sources of each evidentiary item but only its Vietnamese translation. Hence, it remains challenging to obtain a comparative perspective about the conditions of climate across different periods by using these written sources. As shown throughout this article, the main chronicles include the Complete book of the historical records of Đại Việt (大越史記全書‎; Đại Việt sử ký toàn thư) and the Veritable records of Đại Nam (大南實錄‎; Đại Nam thực lục). Some historians have also extracted relevant information from the Imperially commissioned outlines and details of the comprehensive mirror of Vietnamese history (Phan et al., 1856).

If the weather- and climate-related incidents captured in these sources can serve as raw data for past climate time series, then not only does each of the sources provide a discrete set of data but they also contain separate clusters of information. This is because these chronicles were compiled and edited over a long-time span. The Complete book of the historical records of Đại Việt, for instance, was an accumulation of historical information written by several generations of court historians, dating from 1272 to 1697 (Lê et al., 1697; Phung, 2020, p. 522). Thus, the way in which information about the weather and climate of the 13th and 14th centuries was recorded in Vietnamese chronicles can be quite different from, for instance, that of the 17th and 18th centuries. In other words, a high number of recorded drought episodes in a certain period does not immediately suggest that there existed a warmer climate overall.

In addition to dynastic chronicles, Vietnamese archives contain other useful sources, many of which have yet to be included in the study of Vietnamese past climate. These sources include some less-known chronicles such as the Concise summary of Vietnamese historical records (越史略‎; Việt sử lược), the Miscellaneous records of successive dynasties (歷朝雜紀‎; Lịch triều tạp kỷ), and the Sequel to the Historical records of Đại Việt (大越史記續編‎; Đại Việt sử ký tục biên) (Anonymous, c. 1300s, c. 1700s; Cao, c. 1800s). These texts often provide information for contextualization (why and what events were recorded) and/or for cross reference (whether an event was captured by multiple sources). Meteorological observations about weather and climate by both native people and missionaries are also valuable sources. Some studies have cited early modern missionary writings to supplement records of incidents missed in the Vietnamese chronicles (Buckley et al., 2014; Dyt, 2016). Vietnamese sources can sometimes offer similar observations, too. For instance, an aristocrat of the Trần dynasty left behind a poem about a drought episode in the sixth lunar month of 1362 (Đào et al., 1977, pp. 208–209). Finally, many early modern texts containing information about traditional sciences, such as astronomy, agronomy, and medicine, are useful when analyzing the growth of meteorological knowledge and practices in Vietnam. For instance, a sourcebook of Vietnamese traditional farming techniques offers multiple sources relating to premodern meteorology (Trịnh & Nguyễn, 1994).


Like the environmental history of premodern Vietnam, the study of traditional Vietnamese meteorology is an emerging field. The vigorous developments in the paleoclimate science of Vietnam since the beginning of the 21st century have not only facilitated new understandings of the past climate but also motivated research into subject matters often overlooked in Vietnamese studies. This article has analyzed two main aspects of Vietnamese meteorology during the period between around 1000 and the 1850s. Prior to the introduction of colonial/modern meteorology, the Vietnamese maintained distinct meteorological knowledge and practices. In addition, the application of historical analysis and paleoclimate science have helped advance our understanding of meteorology in premodern Vietnam, especially regarding questions that touch on specific weather issues and their importance in past societies.

Like its modern version, meteorology in premodern Vietnam focused on the dynamics of gasses and the efficiency of weather forecasts. But unlike modern meteorology, the links between weather-related phenomena and the impacts of divine forces lay at the core of the investigation. The Vietnamese people also developed techniques to identify the right weather for various activities, including farming and disease prevention. But accuracy of prediction might not have been their utmost goal. The Vietnamese kept meticulous records about past weather incidents, as well as other natural anomalies, because meteorological phenomena were Heaven-sent signs that warned them about cosmological disturbances. Knowing if the weather was proceeding normally or not was essential to keep the universe in balance.

Due to the unique concepts and practices of meteorological knowledge in premodern contexts, there is an urge for a stronger partnership between paleoclimate scientists and historians. On the one hand, crossing instrumental data with historical records often generates more solid reconstructions of the past climate patterns. On the other hand, a deeper level of contextualization helps offer more sophisticated analysis of climate-related information from historical sources, which will stimulate new understanding of the human-climate interactions in the past.

Further Reading