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An intense cold spell has seized a severe and lengthy Arctic outbreak, with thermometers lingering in the minus 20 to minus 40 Celsius range for multiple weeks. On Tuesday, Braeburn in the Yukon recorded -55.7C, marking its chilliest December reading in nearly five decades.

Prolonged Freeze Below -40C

Similarly, the communities of Mayo and Dawson experienced sixteen nights in a row dipping under the minus 40 Celsius threshold, with Mayo plunging to -50.4C on Monday. Whitehorse similarly reported 10 nights when temperatures dropped below -30C.

This Arctic air mass pushed further southward through Christmas week. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

The day after Christmas was forecast to deliver minimum temperatures of at least minus 20C in numerous areas, including Edmonton, Montreal, Ottawa and Quebec.

Likely to Linger into the New Year

The severe cold is forecast to persist through the start of January. There are warnings of possible electrical grid strain in Yukon territory over the next several days, as its energy infrastructure faces unprecedented demand from peak power usage levels.

The prolonged chill has been caused by the Arctic vortex settling across the northern part of the continent this month, which funnels frigid northern air southward. Next week, the cold air mass is expected to retreat north slowly, permitting warmer Pacific winds to flow over the US and into parts of southern Canada.

Pronounced Disparity Compared to Stateside Temperatures

In stark contrast, parts of the US experienced historically high temperatures for Christmas as the mercury climbed roughly 15 to 30 degrees above typical averages. For numerous locations, the weather resembled a spring day in April or May than late December.

Several states set Christmas Day temperature records. The capital of Oklahoma soared to 25C on Christmas Day, surpassing the previous peak of 22C set in 1982. Metropolitan areas such as Austin, Dallas, and Charlotte were also among those that recorded temperatures above 25C.

High-Pressure System Fuels Warmth

Unseasonable heat is predicted to persist through Boxing Day and the days ahead, with atypical high temperatures expected to spread into the south-eastern states later in the week.

This heat is being driven by a robust atmospheric ridge reaching from the arid southwest across the continent, 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. As air sinks through the atmosphere, it compresses and heats further, enabling abnormally high temperatures to develop.