Beginning November 1, 2001, the National Weather Service will be using a revised Wind Chill Chart. The NWS felt the need to have a standardized Index for the US and Canada. The old WCT Index was based on the 1945 Siple and Passel index. This new chart makes use of advances in science, technology, and computer modeling to provide more accurate calculations of winter temperature dangers.

After the February 2001 meetings, Canada and the US agreed on a new wind chill formula which will be the new standard. It is based on the following:

• wind speed calculated at the average height (5 feet) of the human body's face instead of 33 feet (the standard anemometer height);
  
• a human face model;
  
• incorporate modern heat transfer theory (heat loss from the body to its surroundings, during cold and breezy/windy days);
  
• lower the calm wind threshold to 3 mph;
  
• a consistent standard for skin tissue resistance; and
  
• assume the worst case scenario for solar radiation (clear night sky).
  NOTE: In 2002, adjustments for solar radiation for sunny, partly sunny and cloudy days will be added to the calculations
  

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THE NEW CHART

Wind chill temperature is defined as that temperature in calm air which provides the same chilling effect on a person as that for a particular combination of temperature and wind. The chart below allows you to estimate the wind chill temperature for a variety of temperature and wind speeds. For example, if the temperature is 30^oF and wind speed 15 mph, it will feel like it's 19^oF.

Besides being more accurate, the most important feature of this new Wind Chill Index is showing frostbite danger temperatures - an indicator of how to dress properly for winter weather. Wind chill does not affect your car's antifreeze protection or freezing of water pipes, etc. In dressing for cold weather an important factor to remember is that entrapped insulating air warmed by body heat is the best protection against the cold. Consequently, wear loose-fitting, lightweight, warm clothing in several layers. Outer garments should be tightly-woven, water-repellent and hooded. Mittens snug at the wrist are better protection than fingered gloves.