Free Heat Index Calculator
Apparent temperature from heat and humidity.
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Inputs
Result
Heat index
99.7 °F
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Short answer
Apparent temperature from heat and humidity.
What is the Heat Index Calculator?
Apparent temperature from heat and humidity.
How does the Heat Index Calculator work?
Enter the inputs above and read the result.
Formula
Variables
T°FR% humidity
Explanation
Valid roughly T ≥ 80°F, R ≥ 40%.
Examples
Applications
Advantages
Limitations
Common mistakes
Tips
Related concepts
The Heat Index Calculator sits inside the Everyday & Utility Calculators hub, in the weather & environment cluster. Perceived conditions and environmental readings. Understanding the terms below makes the output easier to interpret and easier to compare against neighbouring measures.
Practical use cases and industry applications
Understanding Heat Index
Apparent temperature from heat and humidity. Within everyday & utility calculators, heat index belongs to the weather & environment cluster, where it shares terminology and assumptions with closely related tools.
Learning how heat index is calculated
Valid roughly T ≥ 80°F, R ≥ 40%. Working through the variables one at a time — T, R — makes the result reproducible by hand and easier to sanity-check.
Using heat index to make a decision
Because outputs depend on the assumptions you enter, run more than one scenario before committing to a figure.
How heat index compares with related measures
apparent temperature, humidity, exposure all describe adjacent aspects of weather & environment. Comparing this calculator's output against those measures — using the related tools listed on this page — prevents a single metric from being read in isolation.
Frequently asked questions
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