Heat Index Calculator

Calculate what temperature it feels like to our bodies, based on the current humidity and air temperature, with our free calculator.

Required Information

Results:

What is Heat Index?

Heat index is the temperature that it will feel like after taking into account the current air temperature and either the dew point or humidity.

How to Calculate Heat Index

Calculating the heat index can be done with a quite complicated and long formula. It is as such:

Heat Index Formula

HI = −42.379 + 2.04901523 × T + 10.14333127 × R − 0.22475541 × T × R − 0.00683783 × T2 −0.05481717 × R2 + 0.00122874 × T2 × R + 0.00085282 × T × R2 −0.00000199 × T2 × R2

where HI = Heat Index, T = air temperature, R = relative humidity.

How to Use the Heat Index Calculator

  1. Choose the set of fields you want to work with. By default, you can use temperature and humidity percent, if you change it you can enter the temperature and dew point.

  2. After choosing your fields, enter the appropriate information.

  3. Ensure you selected the correct temperature units when applicable.

  4. Hit calculate and get your results instantly!

Heat Index - Frequently Asked Questions

This means that it will feel like 110 degrees outside in the sun. In the shade this number will be less but in direct sunlight it will feel that hot.

According to the National Weather Service, a heat index between 105 and 129°F is dangerous, while anything 130°F or more is extremely dangerous.

The air temperature needs to be at least 80°F to calculate the heat index.

Create Date: July 26, 2024

Last Modified Date: July 30, 2024

Related Calculators

Escape Velocity Calculator

Calculate the speed at which you will need to travel to escape the pull of a planet or object.

Star Luminosity Calculator

Calculate the level of luminosity of a star based on its temperature and size.

Thin Lens Equation Calculator

Calculate the magnification of a camera lens using the thin lens equation.