Calculate the feels-like temperature and heat risk category
The heat index (also known as the feels-like temperature) measures how hot it really feels when relative humidity is combined with the actual air temperature. This calculator uses the Rothfusz regression equation, the standard method used by the National Weather Service.
Where T is temperature in °F and R is relative humidity in percent. Results are displayed in both °F and °C with a heat risk category.
The NWS categories: Caution (80–90°F) — fatigue possible with prolonged exposure; Extreme Caution (90–103°F) — heat cramps and heat exhaustion possible; Danger (103–124°F) — heat cramps and heat exhaustion likely, heat stroke possible; Extreme Danger (124°F+) — heat stroke highly likely with prolonged exposure.
The heat index accounts for humidity to determine how hot the human body actually feels. High humidity reduces sweat evaporation, making the body feel hotter than the actual air temperature. The heat index can be 15°F or more higher than the actual temperature in humid conditions.