Heat Index Calculator

Combine temperature and humidity to find the actual heat stress level.

Environmental Data

Air Temperature

Relative Humidity

%

Heat Index	Danger Category	Potential Risk
80°F - 90°F	Caution	Fatigue possible
91°F - 103°F	Extreme Caution	Heat stroke/cramps possible
104°F - 124°F	Danger	Heat exhaustion likely
125°F or Higher	Extreme Danger	Heat stroke highly likely

Weather Tips

Input the local temperature and humidity to see how hot it really feels outside.

High humidity prevents sweat from evaporating, which is the body's primary way of cooling itself down.

Drink extra water
Wear light clothing
Take frequent breaks

Heat index values are for shady, light wind conditions. Exposure to full sunshine can increase values by up to 15°F.

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Heat Index Calculator

National Weather Service Danger Levels

Why it Matters

Safety First

Important Note

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