Heat Index Calculator
Calculate Apparent Temperature
Calculate the heat index (apparent temperature) based on air temperature and relative humidity using the NOAA formula.
Weather Parameters
°F
%
About the Formula
Uses NOAA's Rothfusz regression equation, most accurate for temperatures above 80°F (27°C) and humidity above 40%.
Safety Tips
- • Stay hydrated
- • Avoid strenuous activity
- • Stay in shade or AC
- • Check on vulnerable people
Heat Index Categories
80-90°F: Caution
Fatigue possible with prolonged exposure
90-103°F: Extreme Caution
Heat cramps and heat exhaustion possible
103-125°F: Danger
Heat cramps and heat exhaustion likely; heat stroke possible
125°F+: Extreme Danger
Heat stroke highly likely
About Heat Index
The heat index combines air temperature and relative humidity to determine the apparent temperature - how hot it actually feels.
- Higher humidity reduces evaporation
- Reduced evaporation means less cooling
- Body feels hotter than actual temperature
You Might Also Like
Explore more tools in this category
Dress Size Calculator
Calculate women's dress size and convert between US, UK, EU, and AU sizing systems
Capacitance Calculator
Calculate capacitance for parallel, series, plate capacitors, and energy storage
Rainfall Volume Calculator
Calculate water volume from rainfall for rainwater harvesting
Crop Factor Calculator
Calculate crop factor and focal length equivalents for camera sensors
Air Density Calculator
Calculate air density based on temperature, pressure, and humidity
Wind Chill Calculator
Calculate wind chill temperature based on air temperature and wind speed
Carbon Footprint Calculator
Estimate yearly carbon emissions based on travel, electricity, and food habits
Fuel Cost Calculator
Calculate fuel costs for your trips and daily commutes