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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 multiple weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, its coldest December temperature in nearly five decades.

Consecutive Nights of Extreme Cold

Similarly, the communities of Mayo and Dawson experienced 16 consecutive nights colder than minus 40 degrees, with the temperature in Mayo bottoming out at -50.4 degrees Celsius earlier this week. Whitehorse also recorded ten separate 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.

The day after Christmas was forecast to deliver minimum temperatures of at least minus 20C in numerous areas, from Edmonton in the west to Quebec in the east.

Likely to Linger For Days to Come

This harsh winter weather is expected to continue for the foreseeable future. Officials have warned that the Yukon could face electricity outages in the coming days, as the system endures record-high pressure from record-high energy demand.

The lengthy cold snap originates from a stationary polar vortex above Canadian territory through December, enabling a surge of icy Arctic winds to descend. The frigid dome is projected to gradually withdraw north allowing more temperate air from the Pacific to sweep across America and reach into portions of southern Canada.

Pronounced Disparity to American Heat

In stark contrast, parts of the US experienced their warmest Christmas Day on record as temperatures soared about 15-30C above the seasonal average. Across wide regions, the atmosphere was more akin to late spring rather than the end of December.

Several states set Christmas Day temperature records. The capital of Oklahoma soared to 25C on Christmas Day, topping the prior high mark of 22 degrees established over forty years ago. Metropolitan areas such as Austin, Dallas, and Charlotte were also among those that recorded temperatures above 25C.

Heat-Dome Effect Fuels Warmth

Unseasonable heat is predicted to persist for the remainder of the week and beyond, with atypical high temperatures expected to spread into the south-eastern states later in the week.

The warmth has been fuelled by a robust atmospheric ridge extending from the desert south-west towards the north and east, 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. Sinking atmospheric air undergoes compression and additional heating, allowing unusually warm temperatures to build.