The National Weather Service has implemented a new Wind Chill Temperature (WCT) index for the 2001/2002 winter season. The reason for the change is 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.

For over a year there was a discussion within the NWS and MSC about updating the WCT. During the Fall of 2000, a special group (consisting of the National Weather Service, MSC and the International Society of Biometeorology) evaluated the existing wind chill formula and made changes to improve upon it. Chaired by the NWS, the group's goal was to internationally upgrade and standarize the Wind Chill 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:

• usescalculatedwind 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.

T_wc= 35.74 + 0.6215T - 35.75(V^0.16) + 0.4275T(V^0.16)

where

V = Wind Speed in mph

T = Air Temperature in^oF

T_wc= windchill

A wind chill chart is also available for viewing.

Wind Chill Information on NOAA Weather Radio

Note: Wind Chill information for selected cities can be obtained by listening to your local NOAA Weather Radio (NWR) Broadcast. The Wind Chill information is updated every hour. To find which NWR transmitter is closest to you, please visit the NWS Norman NWR page .

Latest Hourly Weather Information for:

Java-based Wind Chill Calculations

If you have a Java-enabled browser and want to calculate your own wind chill values, you can use the java-based wind chill calculators below. The scripts were written by Bryan Ruby of NWSFO Sioux Falls, SD.