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Northern Canada has been gripped by a bitter and extended period of frigid weather, with readings persisting between -20C and -40C for multiple weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, representing its most frigid December day since 1975.

Consecutive Nights Below -40C

Meanwhile, Mayo and Dawson endured sixteen nights in a row below -40C, with Mayo plunging to -50.4C earlier this week. The capital, Whitehorse, likewise saw 10 nights when temperatures dropped below -30C.

This Arctic air mass pushed further southward over the festive period. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

Boxing Day was expected to bring minimum temperatures of at least minus 20C through a wide swath, including Edmonton, Montreal, Ottawa and Quebec.

Expected to Continue Through Early January

The frigid conditions are predicted to linger through the start of January. There are warnings of possible electrical grid strain in Yukon territory in the coming days, as the system endures record-high pressure from record-high energy demand.

The prolonged chill has been caused by the polar vortex remaining anchored across the northern part of the continent this month, which funnels frigid northern air southward. Next week, the cold air mass is expected to retreat north gradually, enabling milder Pacific air to move across America and reach into portions of southern Canada.

Stark Contrast with US Warmth

In stark contrast, parts of the US experienced historically high temperatures for Christmas as the mercury climbed roughly 15 to 30 degrees above typical averages. 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. Metropolitan areas such as Austin, Dallas, and Charlotte also logged readings above 25 degrees Celsius.

Atmospheric Ridge Sustains High Temperatures

Warmer-than-normal conditions are forecast to last for the remainder of the week and beyond, 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, creating a heat-dome effect. This setup creates an extensive zone of high atmospheric pressure blanketing a significant part of the landmass, effectively capping warm air at lower altitudes. Descending air compresses and adiabatically warms, fostering the buildup of exceptional warmth.