Heat Index Calculator

NOAA "feels-like" temperature from air temp and humidity (Rothfusz regression).

Calculator Numbers & Math Updated Apr 20, 2026
How to Use
  1. Enter air temperature and relative humidity.
  2. Result shows heat index and NOAA risk band.
Input
Feels-like

NOAA Risk

Caution
80-90°F — fatigue with prolonged exposure
Extreme caution
90-103°F — heat cramps, heat exhaustion possible
Danger
103-124°F — heat stroke likely with continued activity
Extreme danger
125°F+ — heat stroke imminent

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