Winter Weather Safety and Survival
Wind Chill/Temperature Index
In late 2001, the National Weather Service implemented a new Wind Chill Temperature (WCT) Index. The reason for the change was to improve upon the old index used by the NWS and the Meteorological Services of Canada (MSC) which was based on the 1945 Siple and Passel Index.
The new Wind Chill/Temperature Index makes use of advances in meteorology, biometeorology and computer modeling to provide a more accurate, useful formula for calculating the dangers from winter winds and freezing temperatures. In addition, clinical trials have been conducted and the results of those trials have been used to verify and improve the accuracy of the new formula.
Led by the NWS, implementation of the standarized WCT Index took place throughout the nation and involved the entire meteorological community, and the media, which plays an important role in explaining the index to the general public. In this way, an accurate and consistent measure has been provided to help the public protect itself against the dangers of frostbite and hypothermia. The index has been implemented in Canada and the United States in order to have a consistent WCT Index for North America.
Specifically, the new WCT Index:
- uses calculated wind speeds at an average height of five feet (typical height of a human face) based on readings from the national standard height of 33 feet (typical height of an anemometer);
- is based on the latest heat transfer theory, i.e, .heat loss from the body to its surroundings, during cold and breezy/windy days ;
- and uses a standard factor for skin tissue and assumes a no sunlight scenario.
Twc= 35.74 + 0.6215T – 35.75(V0.16) + 0.4275T(V0.16)
- V = Wind Speed in mph
- T = Air Temperature inoF
- Twc= windchill
A wind chill chart is also available for viewing.
Wind Chill Information on NWS Weather Radio
Note: Wind Chill information for selected cities can be obtained by listening to your local NWS Weather Radio broadcast. The Wind Chill information is updated every hour. To find which NWR transmitter is closest to you, please visit the NWS Norman Weather Radio page.
Latest Hourly Weather Information for:
Products are updated hourly and may include wind chill info for selected sites.
Below is the new wind chill chart from the NWS Headquarters website.