Heat Index Calculator
Calculate perceived apparent heat index using air temperature and relative humidity. Get NOAA heat hazard alerts, safety tips, and direct sunlight offset calculators.
Inputs Configuration
Calculation Output Status
Successfully Solved
How Heat Index Calculator Works
Our high-performance online utility runs entirely client-side, processing your requests securely and instantly inside your web browser. For related features, you can also use our Dew Point Calculator and Btu Calculator tools.
Enter Air Temperature
Provide your parameters or upload your file securely into the workspace.
Set Humidity Level
Our 100% offline-first engine processes the request instantly in browser memory.
Calculate Feels-Like
Download, copy, or print the optimized results instantly with complete privacy.
Heat Safety Levels
Designed for professional results, privacy, and maximum compatibility across all modern desktop and mobile browsers. Enjoy unlimited free calculations without hidden fees.
Frequently Asked Questions About Heat Index
Is this heat index calculator free?
Yes. Calculate apparent temperature with no registration.
Does this include safety alerts?
Yes. Get NOAA heat hazard alerts and safety recommendations.
Can this account for direct sunlight?
Yes. Optionally add direct sunlight offset to the calculation.
Do you store weather data in this calculator?
No. All calculations run locally with complete privacy.