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Wind Chill Calculation
Enter in the Air Temperature in degrees
Fahrenheit and wind speed (mph), then click "Compute WC" to get the old
wind chill (Old WC) and new wind chill (New WC). Thanks to Ron Murphy for
this code.
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About the New Wind Chill Calculation
The National Weather Service, in cooperation with Meteorological
Services of Canada have worked together to develop a wind chill index that is more
representative of the actual conditions felt by the human skin, and to
standardize a formula to be used internationally.
The previous wind chill formula was developed in 1945, and has had no
improvements made to it since its creation. The new wind chill index will
become standard across the United States and Canada starting on November
1, 2001. It was developed through clinical trials with several U.S. and
Canadian Universities, as well as the National Weather Service and Meteorological
Services of Canada.
The new formula makes advances in science, technology, and computer modeling
to provide a more accurate, understandable, and useful formula for calculating
the dangers from winter winds and freezing temperatures. The new index
will be a big change for the National Weather Service as well as for the
public, and will take some getting used to. Some of the things the new
wind chill index will do is:
Use a calculated wind speed at an average height of five feet (typical height of a human face) It is based on a human face model Incorporate modern heat transfer theory, i.e. heat loss from the body to its surroundings during cold and windy days Lower the calm wind threshold from 4 mph to 3 mph Use a consistent standard for skin tissue resistance Assumes no impact from the sun
The standardization of the wind chill index among meteorological communities
is important, so that an accurate and consistent measurement is provided
and public safety is ensured.
In the state of Montana, National Weather Service offices in Billings,
Glasgow and Great Falls have had to change the criteria for issuing wind
chill advisories and wind chill warnings because of the implementation
of this new formula. Under the new formula, "Wind Chill Advisories"
will be issued when the wind is at 10 mph or higher and the wind chill
factor is between 20 to 40 degrees below zero. A "Wind Chill Warning"will
be issued when the wind is 10 mph or higher and the wind chill factor
is 40 degrees below zero or colder.
Color Printable Version of the Wind Chill Chart (.pdf file ~800k - Download Adobe Reader).
Color Printable Version of the Wind Chill Chart (.jpg image ~77k)
National Weather Service Wind Chill Site
National Weather Service Wind Chill
Definitions and Terminology
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www.weather.gov 
