It’s Wind Chill time again in the USA. Recent, below normal temperatures combined with more than usual wind speeds have brought the Wind Chill phenomena to the forefront of most weather forecasts. It means that the wind can make it seem colder than the thermometer says it is – and it is a real phenomenon.
Just what is it? How did it start? Does it pose a real problem or is it just a “passing” fad?
The USA National Weather Service (NWS) has an informative Wind Chill Page online at: www.nws.noaa.gov/om/windchill/. On it it tells us:
The NWS Windchill Temperature (WCT) index uses advances in science, technology, and computer modeling to provide an accurate, understandable, and useful formula for calculating the real dangers from winter winds and freezing and subfreezing temperatures. The index:
- Calculates wind speed at an average height of five feet, typical height of an adult human face, based on readings from the national standard height of 33 feet, typical height of an anemometer
- Is based on a human face model
- Incorporates heat transfer theory, heat loss from the body to its surroundings, during cold and breezy/windy days
- Lowers the calm wind threshold to 3 mph
- Uses a consistent standard for skin tissue resistance
- Assumes no impact from the sun (i.e., clear night sky).
Environment Canada’s Wind Chill web page at: www.ec.gc.ca/meteo-weather/default.asp?lang=En&n=5FBF816A-1 tells even more (It more regularly gets a lot colder there than in the USA – In the Northeast USA we often speak about the “Alberta Clipper‘! Don’t cha know it comes from Canada?)
It’s not just the temperature that chills you, the combination of wind and low temperature produces the effects of much colder temperatures on humans and animals. The wind chill is the effective temperature.
There’s a lot of very useful information on the Environment Canada website including the table below showing the effects of windchill: (Credit: Environment Canada) but we added the temperatures to the nearest degree in F, the preferred units in the warmer, southern portion of the North American continent.)
I believe Continental USA low Temperature Record is – 60 ºF, set in in Tower, Minnesota on February 2, 1996 (Interesting note: your Editor was there and has a thermometer-embellished hat to prove it!)
|Wind Chill||Risk of Frostbite||Other Health
|What to Do|
|0 to -9 ºC (31 to 16 ºF)||Low||
|-10 to -27 ºC (14 to -17 ºF)||Low||
|-28 to -39 ºC (-18 to -38 ºF)||Risk: exposed skin can freeze in 10 to 30 minutes||
|-40 to -47 ºC (-40 to -53 ºF)||High risk: exposed skin can freeze in 5 to 10 minutes*||
|-48 to -54 ºC (-54 to -65 ºF)||Very High risk: exposed skin can freeze in 2 to 5 minutes*||
|-55 ºC (-66 ºF) and colder||Extremely High risk: exposed skin can freeze in less than 2 minutes*||
*In sustained winds over 50 km/h, frostbite can occur faster than indicated.
It is anything but a passing fad, it just gets revisited when Winter rears it frosty head in late Fall every year.
So. we recommend that you bookmark this page and visit it again next year when a serious chill wind blows.