Climatology
This page presents United States's climate context for the current climatology, 1991-2020, derived from observed, historical data. Information should be used to build a strong understanding of current climate conditions in order to appreciate future climate scenarios and projected change. You can visualize data for the current climatology through spatial variation, the seasonal cycle, or as a time series. Analysis is available for both annual and seasonal data. Data presentation defaults to national-scale aggregation, however sub-national data aggregations can be accessed by clicking within a country, on a sub-national unit. Other historical climatologies can be selected from the Time Period dropdown list.
Observed, historical data is produced by the Climatic Research Unit (CRU) of University of East Anglia. Data is presented at a 0.5º x 0.5º (50km x 50km) resolution.
The climate of the United States is highly diverse, ranging from tropical conditions in south Florida and Hawaii to arctic and alpine conditions in Alaska and across the Rocky Mountains. Temperatures for the continental United States show a strong gradient across regions and seasons, from very high temperatures in southern coastal states where the annual average temperatures exceed 21°C, to much cooler conditions in the northern parts of the country along the Canadian border, with seasonal differences as great as 50°C and 10°C, respectively, between summer and winter in the northern Great Plains.
Similarly, precipitation varies across the country and by seasons, measuring more than 127 cm per year along the Gulf of Mexico, while annual precipitation can be less than 30 cm in the Intermountain West and Southwest. The peak rainfall season also varies by region. Many parts of the Great Plains and Midwest experience late-spring peaks, West Coast states have a distinct rainy season during winter, the Desert Southwest is influenced by summer’s North American Monsoon, and many Gulf and Atlantic coastal regions experience summertime peaks. The United States is subject to almost every kind of weather extreme, including severe thunderstorm, almost 1,500 tornadoes per year, and an average of 17 hurricanes that make landfall along the Gulf and Atlantic coasts each decade. At any given time, approximately 20% of the country experiences drought conditions.