Heat Index Calculator
Estimates apparent heat index from air temperature and relative humidity using a standard Fahrenheit regression.
How it works
Heat index estimate
Formula and assumptions
The regression is an estimate intended for hot-weather conditions; it is not a substitute for official local heat alerts. Shade, sunlight, wind, hydration and individual health risks affect heat stress.
Example
Use the sample values, calculate, and change one input at a time.
Frequently asked questions
Are results exact? Results depend on the assumptions and inputs above.
Can I use this for professional decisions? Verify critical results independently.
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Frequently asked questions
Is heat index the same as air temperature?
No. It estimates how hot conditions feel based on temperature and humidity and does not replace official warnings.
What should I check before relying on the result?
Confirm the input units and assumptions described above; independently verify safety-critical, medical, financial or professional decisions.