Most meaningful when T is warm and RH is moderate—see FAQ.
Air temperature (°F) and relative humidity (%)—NWS-style heat index estimate (not a medical device).
Most meaningful when T is warm and RH is moderate—see FAQ.
Dry‑bulb temperature is taken in °F with RH in 0–100% (typical Rothfusz regression with the usual simplifications). Below about 80 °F the page blends toward a simpler heat‑stress estimate; the second line shows an approximate Celsius equivalent of the displayed heat index.
This calculator uses plain decimal numbers. If a result looks wrong, check whether you used a comma instead of a dot (or vice versa) where the field expects one.