Heat Index
What hot weather really feels like once humidity is factored in.
Enter values
°C
%
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Step by step
The formula
NWS Rothfusz regression on temperature and relative humidity
Your body cools by evaporating sweat, and humid air slows that evaporation down. The heat index estimates the dry-air temperature that would feel equivalent, which is why 32°C at 60% humidity feels considerably hotter than 32°C in a desert.
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Example calculations
Common questions this calculator answers — select one to load its values.
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Frequently asked questions
Why does humidity make heat feel worse?+
Your body cools by evaporating sweat. Humid air slows that evaporation, so heat builds up — the heat index estimates the temperature that would feel equivalent in dry air.
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