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Over the years, I have met several people who don't enjoy the term “wind chill”. Some have accused meteorologists of making it up to make us believe it is colder than it is.
Not so. The wind chill index was first developed in 1945 by Antarctic explorers Siple and Passel.
What is it?
The wind chill is the cooling effect of the wind in combination with low temperatures. On a calm day, our bodies insulate us somewhat from the outside temperature by warming up a thin layer of air close to our skin, known as the boundary layer. When the wind blows, it takes this protective layer away, exposing our skin to the outside air. It takes energy from our bodies to warm up a new layer and, if each layer keeps getting blown away, our skin temperature will drop and we will feel colder. Wind also makes you feel colder by evaporating any moisture on your skin – a process that draws more heat away from your body. Studies show that when your skin is wet, it loses heat much faster than when it is dry.
The other day, I received this email from Carl LeGrow from St. John’s NL:
“Let's say the temperature is 0 and the north wind is howling at 80 km/h. Environment Canada says there is NO wind chill. However, if the temperature drops to –1 then they are saying that the wind chill (feels like temp) is -12!!! How is this possible? How can a 1 degree C make a difference of a "feels like temp" of 12 degrees? To me this defies logic. Could you please explain this to me?”
Good observation Carl. You’re right that it doesn’t all of a sudden feel 12 degrees colder. Wind chill “officially” only comes into play when the temperature is below 0 C with a wind speed of more than 10 km/h.
You might also notice that we don't add a degree sign or any other unit after the number used for wind chill. This is because the wind chill is an index; it is calculated, not measured. Even though the wind chill index is calibrated according to the Celsius temperature scale, we do not put C after its value to emphasize the fact that it is not a temperature.
By the way, the coldest wind chill recorded in Canada was at Pelly Bay, Nunavut, on Jan. 13, 1975, when 56 km/h winds made the temperature of –51 C feel more like –92 C!
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Cindy Day is the chief meteorologist for SaltWire Network