How to Calculate Heat Index Calculator
What is Heat Index Calculator?
The heat index (feels-like temperature) combines air temperature and relative humidity to determine the apparent temperature. High humidity impairs the body's ability to cool itself through sweating, making hot conditions feel significantly hotter than the thermometer reads.
Step-by-Step Guide
- 1Uses the Rothfusz regression equation (NWS, USA)
- 2Only applicable when temperature > 27°C (80°F) and humidity > 40%
- 3Below this threshold, the actual temperature is used directly
- 4HI = −42.379 + 2.04901523T + 10.14333127RH − 0.22475541TH − 0.00683783T² − 0.05481717RH² + ...
Worked Examples
Input
35°C (95°F), 70% humidity
Result
Feels like 51°C (124°F)
Extreme danger level
Input
32°C (90°F), 50% humidity
Result
Feels like 38°C (100°F)
Caution — heat cramps possible