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An intense cold spell has seized a bitter and extended period of frigid weather, with readings persisting from 20 to 40 degrees below zero for weeks. On Tuesday, Braeburn in the Yukon recorded -55.7C, marking its chilliest December reading in nearly five decades.

Consecutive Nights in the Deep Minus Forties

Similarly, the communities of Mayo and Dawson experienced sixteen nights in a row below -40C, with Mayo plunging to -50.4C on Monday. Whitehorse similarly reported a series of ten nights when readings fell to minus 30 degrees or lower.

This Arctic air mass pushed further southward over the festive period. Christmas night saw Edmonton's temperatures plummet below minus 28C.

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

The severe cold is forecast to persist into the new year. Authorities have cautioned about potential power failures in the Yukon soon, as the territory’s power grid comes under strain from historically high electricity consumption.

The lengthy cold snap originates from a stationary polar vortex across the northern part of the continent this month, enabling a surge of icy Arctic winds to descend. The frigid dome is projected to gradually withdraw north slowly, permitting warmer Pacific winds to flow over the United States and penetrate southern Canadian regions.

Stark Contrast with US Warmth

Conversely, sections of America recorded 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 than late December.

A number of states broke historical records for December 25th warmth. The capital of Oklahoma soared to 25C on Christmas Day, topping the prior high mark of 22 degrees established over forty years ago. Urban centers like Austin, Dallas, and Charlotte, North Carolina similarly saw thermometers rise past the 25C mark.

Heat-Dome Effect Fuels Warmth

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 extending from the desert south-west towards the north and east, establishing a classic heat-dome pattern. This pattern establishes a broad area of high pressure blanketing a significant part of the landmass, trapping warm air near the surface. Descending air compresses and adiabatically warms, fostering the buildup of exceptional warmth.