Calculators

Heat Index Calculator

Calculate the perceived 'feels-like' temperature from air temperature and humidity using the NWS Rothfusz regression, with heat-stress risk levels

Feels Like
99.7°F
Heat Index (°F)99.7°F
Heat Index (°C)37.6°C
Risk LevelExtreme Caution

Heat cramps and heat exhaustion possible. Continuing activity may lead to heat stroke.

About the Heat Index

  • • Uses the NWS Rothfusz regression with low-humidity and low-temperature adjustments
  • • Most accurate at temperatures ≥ 80°F (27°C) and humidity ≥ 40%
  • • Direct sun exposure can raise the apparent heat index by up to 15°F
  • • Stay hydrated and limit outdoor activity during high heat-index conditions

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