Heat Index Calculator

Calculate the heat index from temperature and humidity

Temperature (°C)

°C

Relative Humidity

Formula (Rothfusz Regression)

HI = -42.379 + 2.049T + 10.14RH - 0.224TRH - 0.0068T² - 0.054RH² + ...

Where T = Temperature (°F), RH = Relative Humidity (%)

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How to Use

What is the heat index?

The heat index is what the temperature feels like to the human body when humidity is factored in with the actual air temperature.

When is heat index important?

Heat index is critical during summer months and heat waves for outdoor workers, athletes, and vulnerable populations.

What danger levels are shown?

The tool classifies heat index into caution, extreme caution, danger, and extreme danger categories with health advisories.