Calculate heat index, feels like temperature, heat risk, humidity effects, estimated dew point, and exposure guidance from air temperature and relative humidity. Use this heat index calculator for summer weather, outdoor work, sports, gardening, hiking, events, and heat safety planning.
Heat index from humidity:
The calculator converts your inputs to Fahrenheit and relative humidity, then applies the standard heat index equation.
Heat risk estimate:
The calculator compares the heat index to common risk ranges and adjusts the practical warning based on sun, activity, breaks, and air movement.
Target feels like temperature:
Enter a target feels like temperature and the calculator estimates the humidity level needed to reach it.
Comparison mode:
Compare the heat index at your main humidity level with a second humidity level to see how much hotter it may feel.
A heat index calculator helps estimate how hot it feels when humidity makes it harder for the body to cool itself through sweat evaporation.
It can be useful for outdoor work, sports, gardening, hiking, events, farming, pets, livestock, school activities, and summer heat planning.
Your result shows the estimated heat index, temperature difference from actual air temperature, heat risk category, exposure guidance, dew point estimate, comparison humidity result, and target humidity estimate when selected. These are planning estimates and should not replace official weather alerts or medical guidance.
Heat index is calculated from air temperature and relative humidity. The standard equation uses temperature in Fahrenheit and humidity as a percentage.
No. Heat index does not change the air temperature. It estimates how hot it feels to the human body when humidity slows cooling.
High humidity reduces how quickly sweat evaporates, making it harder for the body to cool itself.
Yes. High heat index values can increase the risk of heat cramps, heat exhaustion, and heat stroke, especially during hard activity or long exposure.