Estimate what the temperature feels like using air temperature and relative humidity. This heat index calculator shows the apparent temperature in Fahrenheit and Celsius with a simple heat risk guide.
Air temperature:
Enter the current outdoor temperature.
Relative humidity:
Enter the humidity percentage. Higher humidity usually makes hot weather feel hotter.
Temperature unit:
You can enter the temperature in Fahrenheit or Celsius. The calculator converts as needed.
Heat index result:
The result estimates the apparent temperature, or what the air may feel like to the human body.
A heat index calculator is useful for outdoor work, sports, walking, gardening, construction, travel, school activities, and planning around hot weather.
The actual risk can vary based on sun exposure, wind, clothing, hydration, health, and activity level.
Your heat index result estimates what the temperature feels like when humidity is included. For example, a 90°F day can feel much hotter when the humidity is high because moisture in the air slows cooling from sweat evaporation.
Heat index is an estimate of what the temperature feels like when air temperature and relative humidity are combined.
High humidity makes it harder for sweat to evaporate, which makes it harder for the body to cool itself.
Yes. Select Celsius as the temperature unit and the calculator will convert the result to both Celsius and Fahrenheit.
No. Actual temperature is the measured air temperature. Heat index is the feels-like temperature after humidity is included.