WHEN COLD IS COLDER
Wind chill tells the story
It was a pleasant day Saturday with the sun warm on people’s faces, a good day to be outside despite some north wind.
But, according to Environment Canada, that lunchtime temperature of -6 C felt like -13.
We’re obsessed with the wind chill, which is sometimes given on radio forecasts in place of actual temperature. Yet our obsession with wind chill isn’t all it’s cracked up to be.
Canadians are now told that every winter day feels colder than it really is, so that -10 feels like -20, -20 feels like -30, and so on. Colder, it’s always colder.
Here’s the proof: We checked the numbers and Environment Canada records show that every day so far this winter — no exceptions — has officially felt colder than the real temperature.
And the wind chill is not a minor tweak. It often drops “feels like” figures 10 or 12 degrees below the recorded temperatures. There hasn’t been a day this winter when -10 felt like -10.
We looked up all the hourly temperatures since Dec. 21. Here are some observations that show how much difference the wind chill routinely adds:
There is no wind chill calculated
■ when the temperature is above freezing. That leads to oddities like this, from Feb. 5: At 10 a.m. the temperature was 1, and there was no wind chill. Apparently 1 felt like
1. An hour later, though, the temperature dipped to -1, triggering a wind chill measurement that, suddenly, it felt like -10.
(A point of style: We don’t use the symbol C for Celsius in wind chill, because it does not measure actual Celsius degrees. It’s a separate index.)
Similar events happened on Jan. 24, Feb. 1 and Feb. 9, each picking up a dramatic burst of cold as soon as the temperature dipped a fraction of a degree below 0.
Jan. 21 was in the middle of a cold
■
spell, no doubt about that. We had a string of days with temperatures in the minus-20s. On that morning, though, with the thermometer at -23, the wind chill was 15 points colder at -38. It stayed around that level for hours.
So it feels like -38, but what does that feel like? Has Ottawa ever reached -38 in actual temperature? If so, it’s a hugely rare occurrence, yet wind chill measurements tell us it felt that cold over and over in January.
That month alone, we had wind chills of -30 or colder on nine days, with at least two more days at -29.
The actual temperature in Ottawa has not gone below -26 all winter.
Feb. 10 was a day with almost no ■ wind, but it still had a significant wind chill.
The temperature at one point was -15, and the wind chill -17, which sounded reasonable … except that the wind speed was a mere two km/h. That’s not even walking speed. If you walked at two km/h, it would take you half an hour to go a kilometre. Yet that much wind — barely enough to detect — was enough to knock two degrees of the temperature.
February has so far had a high of ■
-8 or warmer every day except one. Yet the wind chills have routinely been measured 10 to 15 degrees colder than that.
Environment Canada has acknowledged the shortcomings of the venerable index.
One problem: Wind chill is calculated in an open area at the airport, well above the ground, which is more exposed and therefore windier than most parts of the city, where there are trees and buildings.
Another: the system doesn’t factor in sunshine. That warmth on your face in late winter is not counted.
Finally, the index is designed to model the effects of cold and wind on bare skin.
For any part of your body covered by clothes or boots, it doesn’t apply.