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An intense cold spell has seized an intense and prolonged cold spell, with thermometers lingering between -20C and -40C for weeks. On Tuesday, Braeburn in the Yukon recorded -55.7C, marking its chilliest December reading in half a century.

Enduring Chill in the Deep Minus Forties

In addition, the locales of Mayo and Dawson suffered through over two straight weeks of nights below -40C, with Mayo plunging to -50.4C earlier this week. The capital, Whitehorse, likewise saw ten separate nights when readings fell to minus 30 degrees or lower.

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

Boxing Day was expected to bring readings no higher than -20 Celsius through a wide swath, including Edmonton, Montreal, Ottawa and Quebec.

Forecast to Persist 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 the territory’s power grid comes under strain from peak power usage levels.

This extended freeze is the result of a stationary polar vortex across the northern part of the continent this month, allowing bitter Arctic air to spill south. The frigid dome is projected to gradually withdraw north slowly, permitting warmer Pacific winds to flow over America and reach into portions of southern Canada.

Dramatic Difference Compared to Stateside Temperatures

Meanwhile, in a dramatic contrast, areas of the United States saw historically high temperatures for Christmas as temperatures soared about 15-30C above the seasonal average. In many areas, conditions felt more typical of April or May rather than the end of December.

Multiple states established new Christmas temperature highs. The capital of Oklahoma soared to 25C on Christmas Day, exceeding the old record of 22C from 1982. Urban centers like Austin, Dallas, and Charlotte, North Carolina were also among those that recorded temperatures above 25C.

Heat-Dome Effect Sustains High Temperatures

Warmer-than-normal conditions are forecast to last for the remainder of the week and beyond, 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 reaching from the arid southwest across the continent, which generates a heat-dome phenomenon. Such a configuration results in a widespread high-pressure system blanketing a significant part of the landmass, effectively capping warm air at lower altitudes. As air sinks through the atmosphere, it compresses and heats further, fostering the buildup of exceptional warmth.