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A prolonged deep freeze has enveloped an intense and prolonged cold spell, with thermometers lingering in the minus 20 to minus 40 Celsius range for multiple weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, its coldest December temperature since 1975.

Prolonged Freeze Below -40C

Meanwhile, Mayo and Dawson endured over two straight weeks of nights colder than minus 40 degrees, with Mayo experiencing a low of -50.4C earlier this week. Whitehorse similarly reported ten separate nights when temperatures dropped below -30C.

This Arctic air mass pushed further southward through Christmas week. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

December 26th was anticipated to usher in minimum temperatures of at least minus 20C through a wide swath, encompassing cities from Edmonton to Quebec.

Expected to Continue Through Early January

The frigid conditions are predicted to linger for the foreseeable future. Authorities have cautioned about potential power failures in the Yukon over the next several days, as the system endures record-high pressure from historically high electricity consumption.

This extended freeze is the result of a stationary polar vortex across the northern part of the continent this month, allowing bitter Arctic air to spill south. Next week, the cold air mass is expected to retreat north allowing more temperate air from the Pacific to sweep across America and reach into portions of southern Canada.

Dramatic Difference Compared to Stateside Temperatures

In stark contrast, parts of the US experienced the hottest December 25th in their history as the mercury climbed roughly 15 to 30 degrees above typical averages. Across wide regions, the atmosphere was more akin to late spring rather than the end of December.

A number of states broke historical records for December 25th warmth. In Oklahoma, Oklahoma City hit 25C on Tuesday, exceeding the old record of 22C from 1982. Urban centers like Austin, Dallas, and Charlotte, North Carolina similarly saw thermometers rise past the 25C mark.

Heat-Dome Effect Fuels Warmth

Warmer-than-normal conditions are forecast to last through Boxing Day and the days ahead, with unseasonable heat forecast to sweep across the southeastern US in the coming days.

This heat is being driven 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 blanketing a significant part of the landmass, which holds warm air close to the ground. As air sinks through the atmosphere, it compresses and heats further, fostering the buildup of exceptional warmth.