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A prolonged deep freeze has enveloped a severe and lengthy Arctic outbreak, with temperatures hovering in the minus 20 to minus 40 Celsius range for weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, its coldest December temperature in nearly five decades.

Consecutive Nights in the Deep Minus Forties

Meanwhile, Mayo and Dawson endured 16 consecutive nights colder than minus 40 degrees, with Mayo plunging to -50.4C on Monday. Whitehorse also recorded 10 nights when temperatures dropped below -30C.

The deep freeze spread farther south over the festive period. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

December 26th was anticipated to usher in lows of at least -20C through a wide swath, from Edmonton in the west to Quebec in the east.

Forecast to Persist Through Early January

The frigid conditions are predicted to linger for the foreseeable future. Officials have warned that the Yukon could face electricity outages in the coming days, as the system endures record-high pressure from historically high electricity consumption.

The lengthy cold snap originates from the polar vortex remaining anchored over Canada for much of December, allowing bitter Arctic air to spill south. In the coming week, forecasts indicate this cold air will pull back northward gradually, enabling milder Pacific air to move across the US and into parts of southern Canada.

Dramatic Difference with US Warmth

In stark contrast, parts of the US experienced their warmest Christmas Day on record as readings skyrocketed 15 to 30 degrees Celsius above normal. In many areas, conditions felt more typical of April or May instead of the heart of winter.

Multiple states established new Christmas temperature highs. The capital of Oklahoma soared to 25C on Christmas Day, 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

Warmer-than-normal conditions are forecast to last through Boxing Day and the days ahead, with abnormal warmth projected to move through the American Southeast soon.

The unseasonable temperatures are powered by a strong upper-level 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, which holds warm air close to the ground. Descending air compresses and adiabatically warms, enabling abnormally high temperatures to develop.