“As the day lengthens, so the cold strengthens.”
~ Early-17th Century proverb

Yes, the sunlight extends into the evenings. Consider it a sign of summer’s eventual return and don’t forgoe your scarf and mittens. They were much needed as a cold front moved through Southern California on Monday, Presidents’ Day. Strong sporadic winds swept across the foothills, while snow fell in local mountains. A winter weather advisory was put into effect for the mountains of Los Angeles, Ventura and Santa Barbara counties. At midnight, here in La Crescenta, it was 38 degrees. The wind’s velocity had weakened to 10 mph. The wind chill factor was 31 degrees. Brrr …

The term “wind chill factor” is frequently used by TV meteorologists and weather reporters. Most of us are pretty certain it pertains to the wind making the already existing cold conditions even colder. This much is true but there is more. First off, there is an interesting story behind the term wind chill factor and then there are the calculating cold science-based facts.

In 1945, Antarctic explorers Paul Siple and Charles Passel devised an index to compare how cold we feel at various temperatures and wind speeds with how cold we feel at the same temperatures in still air. This original wind chill index languished, more or less, until it gained great notoriety during the 1967 Ice Bowl championship game between the Dallas Cowboys and the Green Bay Packers in Green Bay. At game time the temperature was a mere -13F degrees and the wind chill factor was -48F degrees (according to the original index). Formulating and using wind chill factor is now a meteorological standard, thanks to explorers visiting penguins!

Easy version. As wind blows across the exposed surface of our skin, it draws heat away from our bodies. When the wind picks up speed, it draws more heat away, so if your skin is exposed to the wind, your body will cool more quickly than it would have on a still day.

Scientific version. Wind chill = 35.74 + 0.6215T – 35.75(V^0.16) + 0.4275T(V^0.16)
T = air temperature V= wind speed
Here’s a fun and easy link: Wind Chill Calculator
www.wpc.ncep.noaa.gov/html/windchillbody_txt.html

Prepare for a cold and windy at times weather forecast ongoing well into next week. Rain is possible at times, especially Monday through Wednesday. Better add an umbrella to the scarf and mittens!

Sue Kilpatrick is a Crescenta Valley resident and Official Skywarn Spotter for the National Weather Service. Reach her at suelkilpatrick@gmail.com.

  Sue Kilpatrick