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An intense cold spell has seized an intense and prolonged cold spell, with thermometers lingering 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, its coldest December temperature 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 on Monday. Whitehorse similarly reported a series of ten nights when the cold dipped under -30 Celsius.

The deep freeze spread farther south during the holiday season. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

December 26th was anticipated to usher in readings no higher than -20 Celsius in numerous areas, from Edmonton in the west to Quebec in the east.

Forecast to Persist Through Early January

This harsh winter weather is expected to continue through the start of January. Authorities have cautioned about potential power failures in the Yukon soon, as its energy infrastructure faces unprecedented demand from historically high electricity consumption.

The prolonged chill has been caused by the Arctic vortex settling above Canadian territory through December, which funnels frigid northern air southward. The frigid dome is projected to gradually withdraw north allowing more temperate air from the Pacific to sweep across the US and into parts of southern Canada.

Pronounced Disparity to American Heat

In stark contrast, parts of the US experienced the hottest December 25th in their history as the mercury climbed roughly 15 to 30 degrees above typical averages. 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. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, exceeding the old record of 22C from 1982. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina were also among those that recorded temperatures above 25C.

Atmospheric Ridge Fuels Warmth

Above-average warmth is expected to continue through Boxing Day and the days ahead, 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. This pattern establishes a broad area of high pressure over a large portion of North America, effectively capping warm air at lower altitudes. As air sinks through the atmosphere, it compresses and heats further, allowing unusually warm temperatures to build.