The NWS Windchill Temperature (WCT) index uses advances in science, technology, and computer modeling to provide an accurate, understandable, and useful formula for calculating the dangers from winter winds and freezing temperatures. The index:
Calculates wind speed at an average height of five feet, typical height of an adult human face, based on readings from the national standard height of 33 feet, typical height of an anemometer
Is based on a human face model
Incorporates heat transfer theory, heat loss from the body to its surroundings, during cold and breezy/windy days
Lowers the calm wind threshold to 3 mph
Uses a consistent standard for skin tissue resistance
Assumes no impact from the sun (i.e., clear night sky).
Note: Windchill Temperature is only defined for temperatures at or below 50 degrees F and wind speeds above 3 mph. Bright sunshine may increase the wind chill temperature by 10 to 18 degrees F.