Heat Index & Wind Chill

Assessing outdoor weather risks requires looking beyond simple ambient air thermometer readings. In hot weather, elevated relative humidity inhibits the evaporation of human sweat, impairing the body's primary cooling mechanism and making conditions feel dramatically hotter. Conversely, during cold seasons, brisk winds strip away the thin boundary layer of warm air insulating your skin, drastically accelerating heat loss and increasing frostbite susceptibility. You enter the current air temperature in degrees Celsius, the ambient relative humidity percentage, and the prevailing wind speed in miles per hour.

Calculated values appear simultaneously to provide both the heat index and the wind chill equivalent temperature, establishing an accurate benchmark for personal comfort and occupational safety. When interpreting these values, keep in mind that the Rothfusz heat index regression is scientifically calibrated for warm conditions above 26 degrees Celsius, while wind chill equations apply to cold weather at or below 10 degrees Celsius. Additionally, neither calculation accounts for direct solar radiation or wet clothing, which can intensify environmental thermal stress substantially.

Heat index is calculated using the National Weather Service multi-polynomial Rothfusz regression, combining dry-bulb Fahrenheit temperature and relative humidity to model evaporative cooling resistance. Wind chill is determined using the standard NWS regression equation that scales wind velocity raised to the 0.16 power against air temperature. Both resulting values are converted into Celsius to deliver clear apparent temperature metrics.