Heat Index Calculator

The heat index can be used to indicate how an average person will perceive temperature and humidity and the human body ability to cool itself. This tool calculates the heat index in degrees Fahrenheit based on air temperature and relative humidity.

Calculator

Inputs

Results

Heat Index-- °F
Temperature (°F)RH 0%RH 5%RH 10%RH 15%RH 20%RH 25%RH 30%RH 35%RH 40%RH 45%RH 50%RH 55%RH 60%RH 65%RH 70%RH 75%RH 80%RH 85%RH 90%RH 95%RH 100%
80787878787979798080808181828283848485868687
85828282828282838484858688899193959799102104107
90878686868687888991929597100103106109113117122127—
95919090919193949699102105109113118123128134————
1009494959697100102106109114118124129136143——————
1059798100102104108112116121127134141149————————
110100102105108112117122129136143152——————————
115103106110115121127134143152————————————
120105110116122130138148——————————————
125107114121130140————————————————
130108117128——————————————————
135110121———————————————————
140110————————————————————

Heat Stress Categories

Caution - Fatigue is possible with prolonged exposure and/or physical activity

Extreme Caution - Sunstroke, heat cramps and heat exhaustion are possible with prolonged exposure and/or physical activity

Danger - Sunstroke, heat cramps and heat exhaustion are likely. Heat stroke is possible with prolonged exposure and/or physical activity

Extreme Danger - Heatstroke/sunstroke is highly likely with continued exposure

Temperature Conversion

Celsius to Fahrenheit: T (°F) = 9/5 × T (°C) + 32

Fahrenheit to Celsius: T (°C) = 5/9 × (T (°F) - 32)