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An intense cold spell has seized an intense and prolonged cold spell, with temperatures hovering between -20C and -40C for multiple weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, representing its most frigid December day since 1975.

Consecutive Nights of Extreme Cold

In addition, the locales of Mayo and Dawson suffered through 16 consecutive nights dipping under the minus 40 Celsius threshold, with the temperature in Mayo bottoming out at -50.4 degrees Celsius at the start of the week. Whitehorse similarly reported a series of ten nights when temperatures dropped below -30C.

The deep freeze spread farther south during the holiday season. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

The day after Christmas was forecast to deliver lows of at least -20C in numerous areas, from Edmonton in the west to Quebec in the east.

Forecast to Persist For Days to Come

The severe cold is forecast to persist through the start of January. Authorities have cautioned about potential power failures in the Yukon over the next several days, as its energy infrastructure faces unprecedented demand from record-high energy demand.

This extended freeze is the result of the Arctic vortex settling over Canada for much of December, enabling a surge of icy Arctic winds to descend. In the coming week, forecasts indicate this cold air will pull back northward gradually, enabling milder Pacific air to move across America and reach into portions of southern Canada.

Pronounced Disparity with US Warmth

Meanwhile, in a dramatic contrast, areas of the United States saw the hottest December 25th in their history as temperatures soared about 15-30C above the seasonal average. In many areas, conditions felt more typical of April or May than late December.

Several states set Christmas Day temperature records. In Oklahoma, Oklahoma City hit 25C on Tuesday, exceeding the old record of 22C from 1982. Metropolitan areas such as Austin, Dallas, and Charlotte similarly saw thermometers rise past the 25C mark.

Heat-Dome Effect Sustains High Temperatures

Unseasonable heat is predicted to persist through Boxing Day and the days ahead, with abnormal warmth projected to move into the south-eastern states later in the week.

The warmth has been fuelled by a powerful high-altitude ridge stretching from the southwestern deserts northward and eastward, which generates a heat-dome phenomenon. This pattern establishes a broad area of high pressure blanketing a significant part of the landmass, effectively capping warm air at lower altitudes. Sinking atmospheric air undergoes compression and additional heating, fostering the buildup of exceptional warmth.