Heat Index & Real-Feel Calculator
Enter air temperature and relative humidity to estimate a heat index in °F and °C.
A QUICK WALKTHROUGH
How to use this tool
- Enter air temperature in °F or °C.
- Enter relative humidity as a percentage.
- Calculate the estimated heat index and review the formula range.
Formula and range
Uses the NOAA/NWS Rothfusz regression for 80–112 °F (26.7–44.4 °C) and 40–100% relative humidity. Outside that range, the calculator uses the NWS simple adjustment formula and labels the result as an estimate.
What this result means
This is a static calculation from your inputs. It is not an official real-time “feels like” observation, forecast, or health guidance.
Source
National Weather Service, “Heat Index,” describing the Rothfusz regression and simple formula: weather.gov/safety/heat-index.
GOOD TO KNOW
Common questions
Is this an official real-time real-feel temperature?
No. It is a local estimate from the temperature and humidity you enter; it does not use a weather station or live weather feed.
Why is the result an estimate outside the main range?
The Rothfusz regression is intended for 80–112 °F and 40–100% relative humidity. The NWS simple adjustment is used outside that range.
Does this provide health advice?
No. It only calculates an estimated heat index.