A high-pressure system lodged itself over western Ontario late last week and has been funnelling Arctic air southward and driving down temperatures from Atlantic Canada to the Prairies.
“The same high-pressure system is affecting temperatures right across the country,” says Dayna Vettese, a meteorologist at The Weather Network.
“Also, the jet stream is south of us, which allows cooler air to sink further southwards.”
Temperatures in many places, including Toronto, Ottawa, Fredericton and Charlottetown, were almost 15 degrees below seasonal Sunday, and forecast lows for Sunday night approached record-breaking levels.
Parts of the Prairies have also seen record-breaking lows. The temperature dipped to -28.4 in Grand Rapids, Manitoba early Saturday morning, breaking a 1996 record, and several communities in Saskatchewan, including Watrous and Spiritwood, set new low temperature records.
Only British Columbia has been enjoying seasonal temperatures.
The colder temperatures will stick around for a another day or so, with a chilly start to the work week forecast from Edmonton to St. John's.
However, by Tuesday, the high-pressure system begins to shift.
“The pattern starts to break down and temperatures begin to rise closer to seasonal,” Vettese says.