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A prolonged deep freeze has enveloped an intense and prolonged cold spell, with readings persisting from 20 to 40 degrees below zero for multiple weeks. On Tuesday, Braeburn in the Yukon recorded -55.7C, representing its most frigid December day in half a century.

Consecutive Nights Below -40C

Meanwhile, Mayo and Dawson endured 16 consecutive nights below -40C, with Mayo experiencing a low of -50.4C on Monday. Whitehorse also recorded ten separate nights when readings fell to minus 30 degrees or lower.

The bitter chill extended its reach south during the holiday season. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

Boxing Day was expected to bring readings no higher than -20 Celsius across many regions, including Edmonton, Montreal, Ottawa and Quebec.

Expected to Continue into the New Year

The frigid conditions are predicted to linger into the new year. Authorities have cautioned about potential power failures in the Yukon over the next several days, as the system endures record-high pressure from peak power usage levels.

The prolonged chill has been caused by a stationary polar vortex above Canadian territory through December, enabling a surge of icy Arctic winds to descend. Next week, the cold air mass is expected to retreat north gradually, enabling milder Pacific air to move across America and reach into portions of southern Canada.

Stark Contrast Compared to Stateside Temperatures

Meanwhile, in a dramatic contrast, areas of the United States saw historically high temperatures for Christmas as temperatures soared about 15-30C above the seasonal average. In many areas, conditions felt more typical of April or May than late 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 also logged readings above 25 degrees Celsius.

Atmospheric Ridge 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 unseasonable temperatures are powered by a robust atmospheric ridge extending from the desert south-west towards the north and east, 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. As air sinks through the atmosphere, it compresses and heats further, fostering the buildup of exceptional warmth.