Calculate the 'feels like' temperature based on air temperature and relative humidity.
Weather Parameters
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Heat Index Results
Enter temperature and humidity to calculate Heat Index
Quick Reference
80° - 90°FCaution
90° - 103°FExtreme Caution
103° - 124°FDanger
125°F & OverExtreme Danger
Overview
The Heat Index (HI) is an index that combines air temperature and relative humidity to determine the human-perceived equivalent temperature. It's often called 'apparent temperature' or 'feels like' temperature.
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Pro Tips
The Heat Index formula is officially valid for temperatures above 80°F (26.7°C) and humidity above 40%.
Exposure to full sunshine can increase heat index values by up to 15°F (8°C).
Strong winds with very hot, dry air can be extremely dangerous as they increase heat gain.
Always stay hydrated and take breaks in the shade during high heat index conditions.
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Fun Facts
"The Heat Index was developed in 1978 by George Winterling and later adopted by the NWS."
"High humidity makes it feel hotter because it slows down the evaporation of sweat from the skin."
"The highest recorded heat index in the US was 148°F in Appleton, Wisconsin, in 1995."
