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Heat Wave Characteristics in 50 Large U.S. Cities, 1961–2023

Published by U.S. Environmental Protection Agency, Office of Air and Radiation | U.S. Environmental Protection Agency | Metadata Last Checked: January 27, 2026 | Last Modified: 2024-06-14T00:00:00.000+00:00
These maps show changes in the number of heat waves per year (frequency); the average length of heat waves in days (duration); the number of days between the first and last heat wave of the year (season length); and how hot the heat waves were, compared with the local temperature threshold for defining a heat wave (intensity). These data were analyzed from 1961 to 2023 for 50 large metropolitan areas. The size of each circle indicates the rate of change per decade. Solid-color circles represent cities where the trend was statistically significant. For more information: www.epa.gov/climate-indicators

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