Heat Index Calculator
Calculate the heat index (apparent temperature) from temperature and relative humidity using the NWS Rothfusz regression.
Heat index ("feels like")
NWS Rothfusz regression. Most accurate above 80 ยฐF. Indicates the apparent temperature for a given humidity and the risk of heat-related illness.
Frequently Asked Questions
Is the Heat Index Calculator free to use?
Yes, the Heat Index Calculator is 100% free to use. There are no subscriptions, no sign-ups, and no hidden fees.
Is my data safe when using the Heat Index Calculator?
Absolutely. All calculations performed by the Heat Index Calculator happen locally in your web browser. We do not store, track, or transmit your inputs or results to any server.
How accurate is the Heat Index Calculator?
Our Heat Index Calculator uses industry-standard formulas and methodology. You can view the exact formula and calculation logic used in the methodology section above to verify the math yourself.
Can I use the Heat Index Calculator on my mobile phone?
Yes! The Heat Index Calculator is fully responsive and works seamlessly on all devices including smartphones, tablets, and desktop computers.