When is the cold too cold? How extreme cold warnings are issued

“Extreme cold puts everyone at risk.”

At some point each winter, every Canadian will experience cold temperatures. But when temperatures become so cold that they pose a significant risk to people’s health and safety, Environment and Climate Change Canada (ECCC) will issue “extreme cold” warnings.

However, thanks to Canada’s large size and various biomes, what may be considered extreme cold in one part of the country may be very different from another part of the country. So how does ECCC determine when and where to issue extreme cold warnings when what is considered “cold” is so subjective?

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Since there isn’t a standard, overarching definition of “cold” like there is for other winter phenomena—such as blizzards, where conditions must meet the term’s definition for a warning to be issued—ECCC took seasonal climate normals for each region in Canada into account when creating the threshold parameters for extreme cold warnings.

For example, winter in Northern Canada is normally much colder than winter in, say, southern Ontario. What someone in Toronto may consider to feel like extreme cold could be an average winter temperature to someone in Iqaluit.

Frost bite graphic

One overarching parameter is that temperatures must be forecast to stay at or below the extreme cold threshold for at least two hours.

Extreme cold is also measured by both the air temperature and the wind chill. So, somewhere in southern Ontario, the temperature forecast has to feel like -30 or lower for at least two hours for ECCC to issue an extreme cold warning.

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In the north, such as in parts of Nunavut, the forecast needs to call for temperatures to feel like -55 or lower for at least two hours for ECCC to issue a warning.

It’s also important to note that extreme cold warning is different from a cold weather alert. While extreme cold warnings are issued by ECCC at the federal level, municipalities have their own threshold to issue cold weather alerts.

Cold weather alerts essentially sound the alarms for community services such as warming centres to open up for those at risk of prolonged cold exposure.

Even though extreme cold is different throughout the country, it is still a dangerous threat to one’s health and safety. Frostbite and hypothermia are the main concerns when it comes to the extreme cold, and that is why these warnings and alerts are in place.