Heat Index Calculator

Calculate the heat index and what the temperature feels like with humidity factored in using the official NOAA formula.

Heat index is calculated when temperature is 80°F (27°C) or above
Enter relative humidity as a percentage (0-100%)

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See how many Heat Index calculations have been made over time

Understanding Heat Index

What is Heat Index?

Heat index, also known as apparent temperature, is what the temperature feels like to the human body when relative humidity is combined with the air temperature.

The NOAA Formula

We use the official NOAA Rothfusz regression equation, which provides accurate heat index values for temperatures above 80°F with various humidity levels.

Heat Risk Levels

80-90°F: Caution
91-103°F: Extreme Caution
104-125°F: Danger
126°F+: Extreme Danger

Safety Tips

Stay hydrated, wear light clothing, limit outdoor activities during peak heat, seek air-conditioned spaces, and watch for signs of heat exhaustion or heat stroke.

Heat Index Calculator Guides & Articles

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