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A prolonged deep freeze has enveloped a severe and lengthy Arctic outbreak, with temperatures hovering between -20C and -40C for multiple weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, its coldest December temperature in half a century.

Enduring Chill in the Deep Minus Forties

Similarly, the communities of Mayo and Dawson experienced sixteen nights in a row colder than minus 40 degrees, with the temperature in Mayo bottoming out at -50.4 degrees Celsius at the start of the week. The capital, Whitehorse, likewise saw a series of ten nights when temperatures dropped below -30C.

The bitter chill extended its reach south over the festive period. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

The day after Christmas was forecast to deliver minimum temperatures of at least minus 20C through a wide swath, encompassing cities from Edmonton to Quebec.

Likely to Linger 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 territory’s power grid comes under strain from historically high electricity consumption.

The prolonged chill has been caused by the Arctic vortex settling 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 slowly, permitting warmer Pacific winds to flow over the United States and penetrate southern Canadian regions.

Stark Contrast with US Warmth

Meanwhile, in a dramatic contrast, areas of the United States saw the hottest December 25th in their history as readings skyrocketed 15 to 30 degrees Celsius above normal. Across wide regions, the atmosphere was more akin to late spring instead of the heart of winter.

Multiple states established new Christmas temperature highs. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, exceeding the old record of 22C from 1982. Metropolitan areas such as Austin, Dallas, and Charlotte also logged readings above 25 degrees Celsius.

Atmospheric Ridge Fuels Warmth

Unseasonable heat is predicted to persist through Boxing Day and the days ahead, with atypical high temperatures expected to spread across the southeastern US in the coming days.

The warmth has been fuelled by a powerful high-altitude ridge extending from the desert south-west towards the north and east, establishing a classic heat-dome pattern. Such a configuration results in a widespread high-pressure system over a large portion of North America, trapping warm air near the surface. Descending air compresses and adiabatically warms, allowing unusually warm temperatures to build.