Use our precise Heat Index Calculator to quickly determine the "feels like" temperature. Input air temperature and relative humidity to understand the apparent temperature and mitigate heat-related risks. Essential for outdoor activities and workplace safety planning, our tool helps you gauge potential heat stress.
Formula:
The Heat Index (HI) is calculated using a complex multiple regression equation developed by the National Weather Service (NWS) that combines air temperature (T) and relative humidity (RH). The general form of the formula is:
HI = c1 + c2T + c3RH + c4TRH + c5T2 + c6RH2 + c7T2RH + c8TRH2 + c9T2RH2
Where:
- HI = Heat Index (℉ or ℃)
- T = Air Temperature (℉ or ℃)
- RH = Relative Humidity (%)
The specific coefficients (c1...c9) are derived empirically to reflect the human body's perceived temperature.