American cities developed under relatively quiescent climatic conditions. A gradual rise in average global temperatures during the 19th and 20th centuries had a negligible impact on how urban Americans experienced the weather. Much more significant were the dramatic changes in urban form and social organization that meditated the relationship between routine weather fluctuations and the lives of city dwellers. Overcoming weather-related impediments to profit, comfort, and good health contributed to many aspects of urbanization, including population migration to Sunbelt locations, increased reliance on fossil fuels, and comprehensive re-engineering of urban hydrological systems. Other structural shifts such as sprawling development, intensification of the built environment, socioeconomic segregation, and the tight coupling of infrastructural networks were less directly responsive to weather conditions but nonetheless profoundly affected the magnitude and social distribution of weather-related risks. Although fatalities resulting from extreme meteorological events declined in the 20th century, the scale of urban disruption and property damage increased. In addition, social impacts became more concentrated among poorer Americans, including many people of color, as Hurricane Katrina tragically demonstrated in 2005. Through the 20th century, cities responded to weather hazards through improved forecasting and systematic planning for relief and recovery rather than alterations in metropolitan design. In recent decades, however, growing awareness and concern about climate change impacts have made volatile weather more central to urban planning.