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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 an extended duration. On Tuesday, Braeburn in the Yukon recorded -55.7C, marking its chilliest December reading in nearly five decades.

Enduring Chill in the Deep Minus Forties

In addition, the locales of Mayo and Dawson suffered through over two straight weeks of nights colder than minus 40 degrees, with Mayo plunging to -50.4C on Monday. The capital, Whitehorse, likewise saw 10 nights when temperatures dropped below -30C.

The bitter chill extended its reach south during the holiday season. Christmas night saw Edmonton's temperatures plummet below minus 28C.

December 26th was anticipated to usher in lows of at least -20C in numerous areas, encompassing cities from Edmonton to 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 in the coming days, as the system endures record-high pressure 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, enabling a surge of icy Arctic winds to descend. In the coming week, forecasts indicate this cold air will pull back northward gradually, enabling milder Pacific air to move across the United States and penetrate southern Canadian regions.

Dramatic Difference with US Warmth

In stark contrast, parts of the US experienced 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.

A number of states broke historical records for December 25th warmth. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, surpassing the previous peak of 22C set in 1982. Urban centers like Austin, Dallas, and Charlotte, North Carolina were also among those that recorded temperatures above 25C.

Heat-Dome Effect Drives the Heat

Warmer-than-normal conditions are forecast to last for the remainder of the week and beyond, with abnormal warmth projected to move across the southeastern US in the coming days.

This heat is being driven 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 across much of the continent, trapping warm air near the surface. As air sinks through the atmosphere, it compresses and heats further, fostering the buildup of exceptional warmth.