Wind Chill & Heat Index

Calculate apparent temperature from wind chill or heat index using NWS formulas.

Temperature

Must be ≤ 50°F (10°C).

Unit

Wind Speed

Must be greater than 3 mph.

Unit

Wind chill requires temperature ≤ 50°F and wind > 3 mph.

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Feels Like (Wind Chill)

—°F

Danger Levels

Low Risk

> 35°F

Moderate

0 to 35°F

High Risk

-20 to 0°F

Extreme

< -20°F

Documentation

How It Works

This calculator uses the official NWS (National Weather Service) formulas to compute apparent temperature, accounting for wind chill in cold conditions and heat index in hot/humid conditions.

Wind chill uses the 2001 NWS formula based on heat transfer science and wind tunnel testing. Heat index uses the Rothfusz regression with adjustments for extreme humidity.

Formulas

Wind Chill:

WC = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275TV^0.16

Heat Index:

Rothfusz Regression (NWS)

Last Updated: February 28, 2026

Source: National Weather Service (NWS) formulas.

Frequently Asked Questions