Heat Index Calculator
Calculate the “feels like” temperature based on air temperature and humidity
Relative Humidity
Dew Point
Calculate with Humidity
Enter the air temperature and relative humidity to calculate the heat index
°F
%
Calculate with Dew Point
Enter the air temperature and dew point to calculate the heat index
°F
°F
Important Notice
Heat index is only calculated when the temperature is above 80°F (27°C). The formula becomes less accurate above 135°F (57°C).
Feels Like Temperature
100.3°F
The humidity makes it feel 10.3°F hotter than the actual temperature
Caution: Fatigue possible with prolonged exposure
About Heat Index
The heat index is a measure of how hot it really feels when relative humidity is factored in with the actual air temperature.
How it works:
- Your body cools itself by sweating, which evaporates into the air
- High humidity reduces the evaporation rate of sweat
- This makes it feel hotter than the actual air temperature
- The heat index indicates the perceived temperature
Formula used: Heat Index = -42.379 + 2.04901523*T + 10.14333127*RH – 0.22475541*T*RH – 0.00683783*T*T – 0.05481717*RH*RH + 0.00122874*T*T*RH + 0.00085282*T*RH*RH – 0.00000199*T*T*RH*RH
where T = air temperature (°F), RH = relative humidity (%)