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About the Heat Index Calculator
The Heat Index Calculator computes the apparent temperature from air temperature and relative humidity. You enter two values and receive the heat index as the output, expressed in degrees. This number shows how hot conditions actually feel to the human body.
The calculation uses the Rothfusz regression, the standard equation applied by the National Weather Service. It combines the air temperature in Fahrenheit with relative humidity as a percentage through a polynomial expression. Heat index values assume shady, light-wind conditions, so direct sunshine can push the real feel higher. Check the result before planning outdoor work, exercise, or events in warm weather.
- Type the current air temperature into the first field.
- Enter the relative humidity percentage in the second field.
- Read the calculated heat index in the results area.