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The chilling effect of the wind varies with sunshine and each layer of clothing.Mark Blinch/The Globe and Mail

Millions of Canadian weather obsessives spread the lie so easily you'd think they were telling you the Earth is an oblate spheroid.

"It's minus 50 out there!" they'll say, casually omitting that what they're telling you is wind chill – a calculation, not a temperature measurement, invented by North American weather services because their citizens would not accept more scientific methods to tell you to cover up because it is both cold and windy.

Even many weather men and women admit it: They hate the wind chill index, a basic calculation of temperature and wind speed that has spread like a virus and often replaced the actual temperature in weather reports and casual conversation. They hate it because it misleads everyone about how cold it actually is.

"Wind chill is the scourge of most meteorologists because it really skews the picture," said Dave Phillips, senior climatologist at Environment Canada.

Wind doesn't change temperature, but it does blow away the thin layer of warm air that surrounds the skin, hastening frostbite and hypothermia. The problem is that the actual chilling effect of the wind varies with sunshine and each layer of clothing, every shifting gust or wind-breaking building or tree.

A jogger running open-faced into the wind will deal with far greater wind chill than a commuter completely bundled up waiting for a bus in a shelter. Both, however, will freeze to death if the actual temperature is cold enough and they stay outside long enough.

Environment Canada's own system of wind chill warnings exposes the flimsy scientific basis of the system: They will issue a wind chill warning in Southern Ontario when the value hits -30 C. In the North, that number is -55 C. Winnipeg is about halfway in between. If the temperature is -45 C with no wind, no warning at all is issued, even if you'd still likely freeze to death if exposed long enough. (The weather service plans to introduce a catch-all Extreme Cold Warning later this year.)

"What we consider cold and what Vancouver considers cold is very different, even if we freeze at the same rate," said Lori Graham, a CTV weather presenter based in Montreal. "But in my experience, people just want the simplest explanation possible – what makes the most sense to them."

What makes the most sense to people may not be the most scientifically accurate, but wind chill warnings blown out of proportion and spread widely have benefits, according to physicist Miguel Tremblay, who studies wind chill measurements and other environmental issues.

He notes the entire concept of wind chill was developed in the 1940s by scientists working in the Antarctic who never intended it to become a popular forecasting tool. However, it's handy to scare people into adopting "appropriate behaviour corresponding to cold temperatures," Mr. Tremblay said. Besides, he added, "it costs nothing to deploy."

Don't expect Environment Canada to change wind chill calculations any time soon. "Canadians love wind chill," Mr. Phillips said. "It's hard to unite Canadians on any subject, but 82 per cent say they will use wind chill. It's almost become personal for them."

Like many tales of Canadian unity, this one reached a turning point in the 1980s. At the time, three distinct indexes of wind chill were in use in the Maritimes, Prairies, and Ontario and Quebec.

A grand experiment was run on the Prairies and in the North to move away from the "-25 C, feels like -37 C" method of measuring chill from wind, into actually measuring how much heat was lost each second over a given surface. However, in places such as Winnipeg this produced weather reports only a science geek could love: "The temperature is -28 C, with a wind chill of 3,000 watts per square metre."

Prairie people accepted the change with their stereotypical stoicism. While "wind chill of 3,200" seems meaningless to most, "farmers would know to go check on their cows in the barn and teachers knew when to cancel recess," Mr. Phillips said. "They took it as a point of pride they were willing to adapt to something more scientific."

But weather fanatics in the East revolted at the new science, and what ensued was a crumbling of national standards.

In Atlantic Canada, wind chill was reported by how many minutes it would take for skin to freeze. (This is a system favoured by Mr. Tremblay, the physicist, not because of scientific value but because it is more useful. It's a number often passed along by presenters such as Ms. Graham, but isn't an official part of Environment Canada forecasts.)

In Ontario and Quebec, people held on to an even more rudimentary calculation than the one used today to say "the temperature is -34 C, feels like -60 C."

"We let the regions use what they want," Mr. Phillips said. "That was a mistake."

In the 1990s, weather experts in Canada and the United States came up with an initial version of the current system. It exaggerated wind chill even more, Mr. Phillips said. "It assumed the exposed person was nude sitting on a park bench," he said. Business people who rely on clients braving cold, such as ski hill operators, demanded the calculation be toned down, Mr. Phillips said. "People were cancelling reservations! Now we at least presume the person is properly clothed and not sedentary."

Canadians have long told themselves lies and misinformation about the weather.

Many early settlers in Eastern Canada believed it would warm up if there were fewer trees around. Montreal, after all, is at a latitude south of mild Paris. They appeared to be unaware of the effects of ocean and upper air currents, Mr. Phillips said.

In the 1800s, when Canada was trying to draw pioneers, government salesmen would go to Europe to try to draw out immigrants with instructions to omit only one word in their presentations to packed halls: cold. Once in Canada, hundreds of those immigrants died of hypothermia each winter.

"Even into the 1930s," Mr. Phillips said, "the papers would have stories that read like sports scores with death tolls."

Today, nobody can say they are not warned.


Colder than Mars

Tuesday, Dec. 31, was the coldest day in Winnipeg in 80 years, with temperatures plunging early in the day to -37.9 C. With the wind chill added, it felt like -48 C. It hasn't been that cold in Winnipeg in December since 1933, and it was so cold it was warmer on Mars. "According to the Curiosity Rover, Mars reached a maximum air temperature of -29°C today," the Manitoba Museum posted on Twitter. "Winnipeg's high was -31°C."

Canada's all-time cold

On Feb. 3, 1947, the weather station at Snag near the Alaska Highway in western Yukon recorded the coldest temperature ever in North America, -63 C. Back then the village boasted a population of a few dozen natives, fur traders and military airport personnel. That 1947 cold snap set record lows across Canada, including -54.4 C in Norman Wells, NWT, and -50.6 C in Fort McMurray, Alta. Saturday's forecast for the now-unpopulated Snag? -16 C.

Canada's first weatherman

On a very cold late December night in 1794 in York Factory, Man., Peter Fidler, a Hudson's Bay Company man and one of Canada's first weather observers, recorded that gin froze solid at -27 C, brandy at -32 C and rum at -35 C.

When Great Lakes freeze over

The relatively shallow Lake Erie, Lake Michigan and Lake Huron freeze over once every several decades. But for the deeper Lake Ontario and the even deeper Lake Superior, freezing over is rare. Newspaper reports say Lake Ontario froze over in 1875 and 1934. "The cold wave left in its wake a series of events unprecedented in the memory of most," The Globe reported in 1934. "The 45-mile stretch between Cobourg and Rochester, N.Y., was a solid mass of ice."

Frost quakes

Eastern Canada's current extreme cold snap has been a bang. Or, to use the more scientific term, a cryoseism. These frost quakes occur when rapidly declining temperatures cause moisture trapped in cracks in the ground to rapidly freeze and expand. As pressure is released, it can cause fissures, cracks and loud banging sounds. "Very rare, very cool, but very scary," says CBC meteorologist Jay Scotland.

Coldest place, on average

Eureka, a small research base on Nunavut's Ellesmere Island, is officially Canada's coldest weather station. The average annual temperature is -19.9 C, but in February, usually the coldest month, Eureka's average temperature is -38.4 C. In February, 1979, Eureka recorded the lowest average monthly temperature in North America, -47.9 C. For 18 days, temperatures stayed below -45 C. On Feb. 15, the station also surpassed its previous all-time low with a recording of -55.3 C.

Sources: Wire services, Canadian Encyclopedia

Editors note: This is a corrected version of this story. An earlier version incorrectly placed York Factory in Ontario.

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