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An intense cold spell has seized a severe and lengthy Arctic outbreak, with readings persisting between -20C and -40C for multiple weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, marking its chilliest December reading in nearly five decades.

Prolonged Freeze 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. Whitehorse also recorded ten separate nights when temperatures dropped below -30C.

The bitter chill extended its reach south over the festive period. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

December 26th was anticipated to usher in lows of at least -20C in numerous areas, including Edmonton, Montreal, Ottawa and Quebec.

Expected to Continue Through Early January

This harsh winter weather is expected to continue into the new year. Officials have warned that the Yukon could face electricity outages over the next several days, as the system endures record-high pressure from peak power usage levels.

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. In the coming week, forecasts indicate this cold air will pull back northward gradually, enabling milder Pacific air to move across the United States and penetrate southern Canadian regions.

Stark Contrast with US Warmth

Meanwhile, in a dramatic contrast, areas of the United States saw the hottest December 25th in their history as the mercury climbed roughly 15 to 30 degrees above typical averages. For numerous locations, the weather resembled a spring day in April or May rather than the end of December.

A number of states broke historical records for December 25th warmth. In Oklahoma, Oklahoma City hit 25C on Tuesday, 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.

Atmospheric Ridge Sustains High Temperatures

Unseasonable heat is predicted to persist through Boxing Day and the days ahead, with atypical high temperatures expected to spread through the American Southeast soon.

The warmth has been fuelled by a robust atmospheric ridge stretching from the southwestern deserts northward and eastward, establishing a classic heat-dome pattern. Such a configuration results in a widespread high-pressure system over a large portion of North America, effectively capping warm air at lower altitudes. Descending air compresses and adiabatically warms, allowing unusually warm temperatures to build.