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An intense cold spell has seized a severe and lengthy Arctic outbreak, with readings persisting in the minus 20 to minus 40 Celsius range for an extended duration. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, marking its chilliest December reading in half a century.

Enduring Chill in the Deep Minus Forties

Similarly, the communities of Mayo and Dawson experienced 16 consecutive nights dipping under the minus 40 Celsius threshold, with the temperature in Mayo bottoming out at -50.4 degrees Celsius on Monday. Whitehorse similarly reported 10 nights when readings fell to minus 30 degrees or lower.

The deep freeze spread farther 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 in numerous areas, including Edmonton, Montreal, Ottawa and Quebec.

Expected to Continue For Days to Come

The frigid conditions are predicted to linger through the start of January. There are warnings of possible electrical grid strain in Yukon territory over the next several days, as the system endures record-high pressure from historically high electricity consumption.

This extended freeze is the result of the polar vortex remaining anchored above Canadian territory through December, which funnels frigid northern air southward. In the coming week, forecasts indicate this cold air will pull back northward gradually, enabling milder Pacific air to move across America and reach into portions of southern Canada.

Stark Contrast with US Warmth

Meanwhile, in a dramatic contrast, areas of the United States saw their warmest Christmas Day on record as the mercury climbed roughly 15 to 30 degrees above typical averages. Across wide regions, the atmosphere was more akin to late spring rather than the end of December.

A number of states broke historical records for December 25th warmth. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, 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 Fuels Warmth

Warmer-than-normal conditions are forecast to last on December 26th and into the weekend, with atypical high temperatures expected to spread into the south-eastern states later in the week.

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. This setup creates an extensive zone of high atmospheric pressure across much of the continent, trapping warm air near the surface. As air sinks through the atmosphere, it compresses and heats further, allowing unusually warm temperatures to build.