Heat Index Calculator

The perceived heat, the heat index, can be calculated from actual temperature and humidity. This is a subjective value for the sensation of warmth above about 20°C. The higher the humidity, the greater the perceived heat; dry heat is easier to bear. The humidity can be read from a hygrometer. The wind speed plays no role in the perceived warm temperature, but it does in the cold; see perceived temperature. A heat index of around 40°C or higher is considered dangerous. In extreme cases, values ​​of up to 70°C can occur in nature. Please enter the actual temperature in degrees Celsius and the humidity in percent; the heat index, i.e. the perceived heat in degrees Celsius, will be calculated. This is a subjective value for the perception of heat above about 20°C. However, this subjective sensation is biologically based, as the body is less able to cool down in high humidity than in low humidity and therefore overheats more quickly. The greater the humidity, the greater the perceived heat; dry heat is easier to bear. Humidity can be measured with a hygrometer. The wind speed does not play a role for warm felt temperature, but it does for cold, for this see windchill. In contrast to the heat index, however, the humidity is irrelevant for the windchill. A heat index from around 40°C is considered dangerous, and even lower values ​​over longer periods. In extreme cases, values of over 70°C can occur in nature.
Please enter the actual temperature in degrees Celsius and the humidity in percent; the heat index, i.e. the perceived heat in degrees Celsius, will be calculated.

The formula for the calculation is h = -8.784695 + 1.61139411*t + 2.338549*f - 0.14611605*t*f - 0.012308094*t² - 0.016424828*f² + 0.002211732*t²*f + 0.00072546*t*f² - 0.000003582*t²*f²
h = heat index in degrees Celsius , t = real temperature in degrees Celsius, f = humidity in percent

Example: at 30 degrees Celsius and 80 percent humidity, the heat index is almost 38 degrees Celsius. At the same temperature and only 20 percent humidity, however, the heat index is just over 28 degrees Celsius.

As climate change progresses, the heat index will become increasingly relevant information and life-threatening conditions will become more frequent. Climate change is fueled by greenhouse gases (especially carbon dioxide), which are mainly produced by the combustion of fossil fuels (coal, oil, natural gas). For more information, see Global warming caused by CO₂. Other values ​​related to the heat index are the dew point and the wet bulb temperature.

Physics commonly uses SI units. Here is a calculator to convert lengths, temperature, pressure, speed and other units.