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An intense cold spell has seized an intense and prolonged cold spell, with temperatures hovering in the minus 20 to minus 40 Celsius range for weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, marking its chilliest December reading in half a century.

Consecutive Nights Below -40C

In addition, the locales of Mayo and Dawson suffered through sixteen nights in a row dipping under the minus 40 Celsius threshold, with Mayo experiencing a low of -50.4C at the start of the week. Whitehorse also recorded ten separate nights when the cold dipped under -30 Celsius.

The bitter chill extended its reach south over the festive period. 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, from Edmonton in the west to Quebec in the east.

Expected to Continue into the New Year

This harsh winter weather is expected to continue into the new year. There are warnings of possible electrical grid strain in Yukon territory soon, as its energy infrastructure faces unprecedented demand from historically high electricity consumption.

The lengthy cold snap originates from the polar vortex remaining anchored over Canada for much of December, which funnels frigid northern air southward. In the coming week, forecasts indicate this cold air will pull back northward gradually, enabling milder Pacific air to move across the US and into parts of southern Canada.

Pronounced Disparity with US Warmth

Meanwhile, in a dramatic contrast, areas of the United States saw the hottest December 25th in their history as temperatures soared about 15-30C above the seasonal average. In many areas, conditions felt more typical of April or May than late December.

A number of states broke historical records for December 25th warmth. The capital of Oklahoma soared to 25C on Christmas Day, surpassing the previous peak of 22C set in 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

Warmer-than-normal conditions are forecast to last on December 26th and into the weekend, with atypical high temperatures expected to spread through the American Southeast soon.

The warmth has been fuelled by a robust atmospheric ridge extending from the desert south-west towards the north and east, creating a heat-dome effect. Such a configuration results in a widespread high-pressure system 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, enabling abnormally high temperatures to develop.