ZovaTool

Heat Index Calculator

Heat Index
99.7°F
37.6°C • Extreme Caution

Heat Index Chart (°F)

T \ RH40%50%60%70%80%90%
80°808182838486
84°838588909498
88°889195100106113
92°9499105112121131
96°101108116126138152
100°109118129143158176
104°119131145161181202
108°130144162182205231

How to use the Heat Index Calculator

  1. Enter air temperature (°F) and relative humidity (%).
  2. Read heat index in °F and °C with a danger level.
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Humidity makes hot feel hotter

High humidity prevents sweat from evaporating, so your body can't cool itself. 95°F at 70% RH feels like 124°F.

NWS danger thresholds: 80–90 Caution, 90–103 Extreme Caution, 103–124 Danger, 125+ Extreme Danger.