Extension Ag Update
November/December 2003
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Not Feeling Quite So Cold?

Ellen Phillips, Extension Educator Crop Systems, Countryside Extension Center, ephillips@uiuc.edu, (708) 352-0109

Wind chill factors are used to estimate how cold the weather feels. If it is 20 degrees Fahrenheit with a 10 mile per hour wind, it feels as if it were 2 degrees above zero with no wind. The faster the wind speed the colder it feels outside. Are you are feeling warmer now than a couple of years ago? It may be due to a new wind chill equation that the National Weather Service has been using for calculating the wind chill the last couple of years. The new formula does not estimate as great a drop in temperature as the previous equation predicted.

Specifically, the new WCT index: uses calculated wind speed at an average height of five feet. This would be the typical height of an adults face. This wind speed is calculated based on readings from the national standard height of 33 feet (typical height of an anemometer). The assumptions are based on the latest heat transfer theory relating heat loss from the body to its surroundings on a cold and windy day. Wind chill calculations also do not take into account sunlight. If you want to try your hand at calculating the wind chill where you are, try using the NWS Wind Chill equation below:

Wind Chill (oF) = 35.74 + 0.6215T - 35.75(V0.16) + 0.4275T(V0.16)

  • Where, T = Air Temperature (oF)
  • V = Wind Speed (mph)

To learn more about wind chill, visit the National Weather Service Wind Chill page at:

http://www.srh.noaa.gov/jan/wchill.html

As temperatures drop or wind speed increases, the potential for health problems increase. Frostbite develops at freezing temperatures and can occur more quickly if the skin is wet. Frostbite is damage done when the skin tissue freezes. Frostbite causes a loss of feeling and a white or pale appearance in extremities such as fingers, toes, ear lobes or the tip of the nose. Keep safe this winter season by dressing warmly with many layers, change clothing that gets wet and keep out of the wind when possible.