About Heat Stress Maps
Heat stress is defined as a nighttime (8:00 pm through 8:00 am) hour when the sum of the temperature (°F) and Relative Humidity (%) exceeds 150. On a daily basis, high risk corresponds to five or more heat stress hours. Low risk days have fewer than two heat stress hours. Moderate risk occurs otherwise.
On the weekly maps, red dots generally indicate weeks with at one or more high heat stress days or consistent (typically more than 4 days) moderate risk. Weeks with low risk have no moderate risk days. Moderate weekly risk is indicated otherwise.
Forecast maps are based on National Weather Service forecast guidance.