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An intense cold spell has seized a severe and lengthy Arctic outbreak, with temperatures hovering from 20 to 40 degrees below zero for an extended duration. On Tuesday, Braeburn in the Yukon recorded -55.7C, its coldest December temperature in nearly five decades.

Consecutive Nights of Extreme Cold

Meanwhile, Mayo and Dawson endured 16 consecutive nights below -40C, with Mayo plunging to -50.4C at the start of the week. The capital, Whitehorse, likewise saw a series of ten nights when the cold dipped under -30 Celsius.

The bitter chill extended its reach south during the holiday season. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

Boxing Day was expected to bring readings no higher than -20 Celsius through a wide swath, from Edmonton in the west to Quebec in the east.

Forecast to Persist Through Early January

This harsh winter weather is expected to continue for the foreseeable future. There are warnings of possible electrical grid strain in Yukon territory over the next several days, as its energy infrastructure faces unprecedented demand from historically high electricity consumption.

This extended freeze is the result of a stationary polar vortex above Canadian territory through December, enabling a surge of icy Arctic winds to descend. The frigid dome is projected to gradually withdraw north allowing more temperate air from the Pacific to sweep across the US and into parts of southern Canada.

Stark Contrast Compared to Stateside Temperatures

Meanwhile, in a dramatic contrast, areas of the United States saw 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 than late December.

A number of states broke historical records for December 25th warmth. In Oklahoma, Oklahoma City hit 25C on Tuesday, surpassing the previous peak of 22C set in 1982. Metropolitan areas such as Austin, Dallas, and Charlotte similarly saw thermometers rise past the 25C mark.

Heat-Dome Effect Fuels Warmth

Above-average warmth is expected to continue on December 26th and into the weekend, with unseasonable heat forecast to sweep across the southeastern US in the coming days.

This heat is being driven by a powerful high-altitude ridge stretching from the southwestern deserts northward and eastward, establishing a classic heat-dome pattern. This pattern establishes a broad area of high pressure blanketing a significant part of the landmass, effectively capping warm air at lower altitudes. As air sinks through the atmosphere, it compresses and heats further, allowing unusually warm temperatures to build.