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Northern Canada has been gripped by a bitter and extended period of frigid weather, with readings persisting between -20C and -40C for weeks. On Tuesday, Braeburn in the Yukon recorded -55.7C, its coldest December temperature since 1975.

Enduring Chill in the Deep Minus Forties

Meanwhile, Mayo and Dawson endured over two straight weeks of nights dipping under the minus 40 Celsius threshold, with Mayo plunging to -50.4C earlier this week. Whitehorse similarly reported ten separate nights when the cold dipped under -30 Celsius.

The deep freeze spread farther south through Christmas week. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

Boxing Day was expected to bring lows of at least -20C in numerous areas, including Edmonton, Montreal, Ottawa and Quebec.

Likely to Linger Through Early January

This harsh winter weather is expected to continue through the start of January. There are warnings of possible electrical grid strain in Yukon territory soon, as the system endures record-high pressure from record-high energy demand.

This extended freeze is the result of a stationary polar vortex over Canada for much of December, which funnels frigid northern air southward. The frigid dome is projected to gradually withdraw north gradually, enabling milder Pacific air to move across the United States and penetrate southern Canadian regions.

Stark Contrast with US Warmth

In stark contrast, parts of the US experienced their warmest Christmas Day on record as the mercury climbed roughly 15 to 30 degrees above typical averages. In many areas, conditions felt more typical of April or May rather than the end of December.

Multiple states established new Christmas temperature highs. In Oklahoma, Oklahoma City hit 25C on Tuesday, surpassing the previous peak of 22C set in 1982. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina similarly saw thermometers rise past the 25C mark.

Atmospheric Ridge Fuels Warmth

Warmer-than-normal conditions are forecast to last through Boxing Day and the days ahead, with abnormal warmth projected to move across the southeastern US in the coming days.

The warmth has been fuelled by a robust atmospheric ridge extending from the desert south-west towards the north and east, creating a heat-dome effect. This setup creates an extensive zone of high atmospheric pressure across much of the continent, effectively capping warm air at lower altitudes. As air sinks through the atmosphere, it compresses and heats further, fostering the buildup of exceptional warmth.