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Northern Canada has been gripped by a severe and lengthy Arctic outbreak, with readings persisting between -20C and -40C for weeks. On Tuesday, Braeburn in the Yukon recorded -55.7C, representing its most frigid December day in nearly five decades.

Prolonged Freeze of Extreme Cold

In addition, the locales of Mayo and Dawson suffered through over two straight weeks of nights dipping under the minus 40 Celsius threshold, with Mayo plunging to -50.4C at the start of the week. Whitehorse similarly reported a series of ten nights when readings fell to minus 30 degrees or lower.

This Arctic air mass pushed further southward during the holiday season. Christmas night saw Edmonton's temperatures plummet below minus 28C.

The day after Christmas was forecast to deliver readings no higher than -20 Celsius across many regions, 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 soon, as the territory’s power grid comes under strain from peak power usage levels.

The lengthy cold snap originates from the Arctic vortex settling across the northern part of the continent this month, which funnels frigid northern air southward. The frigid dome is projected to gradually withdraw north 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 historically high temperatures for Christmas 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.

A number of states broke historical records for December 25th warmth. The capital of Oklahoma soared to 25C on Christmas Day, topping the prior high mark of 22 degrees established over forty years ago. Urban centers like Austin, Dallas, and Charlotte, North Carolina similarly saw thermometers rise past the 25C mark.

High-Pressure System Sustains High Temperatures

Above-average warmth is expected to continue on December 26th and into the weekend, with abnormal warmth projected to move across the southeastern US in the coming days.

The warmth has been fuelled by a robust atmospheric ridge extending from the desert south-west towards the north and east, which generates a heat-dome phenomenon. This setup creates an extensive zone of high atmospheric pressure across much of the continent, effectively capping warm air at lower altitudes. Sinking atmospheric air undergoes compression and additional heating, allowing unusually warm temperatures to build.