Maps
Annualized Frequency [P]
Risk Score [P]
Data Sources
Further Information
These maps display the annualized frequency and risk scores of heat waves in 2025.
A heat wave is defined as a period of abnormally and uncomfortably hot and unusually humid weather, typically lasting two or more days, with temperatures outside historical averages for a given area.†† As such, this is a measure of relative (not absolute) temperature.
High heat in combination with high humidity poses a serious risk to health, with wet bulb temperatures over 88 °F considered a critical threshold for human survival.† Climate change is projected to greatly increase the number of people exposed to heat wave events in the coming decades.†
