Heat Index Calculator
NOAA "feels-like" temperature from air temp and humidity (Rothfusz regression).
How to Use
- Enter air temperature and relative humidity.
- Result shows heat index and NOAA risk band.
Show Work
NOAA Risk
About the Heat Index Calculator
Whether you are at a desk or on your phone, the Heat Index Calculator makes everyday maths and number work easy — and it is completely free. NOAA "feels-like" temperature from air temp and humidity (Rothfusz regression).
How it works
Type your numbers into the boxes. The answer shows up right away — you do not have to press a button. If you change a number, the answer changes too. So you can try different numbers and watch what happens, or check an answer you worked out yourself. Just make sure each box has the right kind of number in it.
Want the deeper story? The Knowledge Base explains the ideas behind the tools in more detail.
Frequently Asked Questions
How do I use the Heat Index Calculator?
Just type your numbers. The answer shows up right away — there is no button to press. Change anything and it updates by itself.
Is it free? Does it work without internet?
Yes to both. It is free with no sign-up, and once the page has loaded it keeps working even with no internet.
Where does my data go?
Nowhere — every calculation runs on your own device. Nothing you enter is uploaded, logged, or stored.
Common Use Cases
Nothing to set up
Open the page and start. There is nothing to install, and no account to make.
Check your work
Worked it out yourself? Use the Heat Index Calculator to make sure your answer is right.
Learn while you do it
Seeing what you put in and what comes out helps you understand how they fit together.
Safe and private
Everything you type stays on your device. Nothing is sent to a server or saved.
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