What wind chill and weather warnings really mean, according to a meteorologist

Environment Canada meteorologist Brian Proctor explains exactly how weather warnings get issued, and how they work.

How those warnings get issued and how they work

Extreme cold warnings are issued in Alberta when the temperature drops to -40 C or below. (Sean Kilpatrick/Canadian Press)

For most Canadians, extreme cold warnings are a good excuse to stay indoors, bundle up under some warm quilts, and Google search flights to anywhere nearer to the equator than here.

Environment Canada meteorologist Brian Proctor sat down with CBC News to explain exactly how those warnings get issued, and how they work.

What has to happen to issue a weather warning?

For Alberta, an extreme cold weather warning gets issued once either the temperature or wind chill drop to -40 C or colder, but the temperature required to issue a warning actually differs depending on the region of Canada, based on what is climatologically normal for that area.

"People that live in Yellowknife, Dawson City or Iqaluit are used to experiencing very cold weather temperatures and they're more acclimatized to being able to deal with those kinds of temperatures," Proctor said.

Even people in northern Alberta communities like High Level or Fort McMurray are better equipped with knowing how to dress for sub-zero weather, and have infrastructure that's built for the weather, than citizens of warmer regions like the Okanagan. 

"It's really about what people's experiences are."

Have the temperature values for weather alerts ever been changed?

Environment Canada used to issue wind chill warnings for communities on the Hudson's Bay when temperatures would dip to -40 C, but then they realized that the warnings were going out too frequently, and people were simply used to that level of cold, Proctor said.

Now, it takes a frigid -40 C to -50 C to trigger an alert in that region.

In Churchill, Man., the weather needs to dip well below -40 C for a weather alert to be issued. (Cameron MacIntosh/CBC)

Right now, it's the heat warning criteria that's being adapted and changed across the country.

Environment Canada is working with partners like Alberta Health to do an analysis of what temperatures are causing health issues, as well as analyzing what temperatures people in different regions usually experience.

What is wind chill, anyway?

Wind chill is worth paying attention to more than the actual temperature outside, because the discrepancy can often lead to problems like hypothermia or frost bite. 

"Wind chill indicates that the temperature your body is going to be experiencing or feeling is actually colder than the actual temperature," Proctor said.

He explained that people generate heat that's supposed to surround the body and keep you warm.

Wind chill can pose a risk to health, like hypothermia or frost bite. (Jeff McIntosh/The Canadian Press)

But, if a person is out in a windy environment, it takes the heat from the body and carries it away.

"What the consequence of that is, is your body begins to feel colder than it really is and experience lower temperatures than what the air temperature around your body really would be," said Proctor. 

It's not an exact measurement, so that's why wind chill is often expressed as the "feel" of a temperature if there was no wind.