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Northern Canada has been gripped by a severe and lengthy Arctic outbreak, with temperatures hovering in the minus 20 to minus 40 Celsius range for multiple weeks. On Tuesday, Braeburn in the Yukon recorded -55.7C, its coldest December temperature in nearly five decades.

Consecutive Nights in the Deep Minus Forties

Similarly, the communities of Mayo and Dawson experienced 16 consecutive nights colder than minus 40 degrees, with Mayo experiencing a low of -50.4C on Monday. The capital, Whitehorse, likewise saw ten separate nights when temperatures dropped below -30C.

This Arctic air mass pushed further southward during the holiday season. Christmas night saw Edmonton's temperatures plummet below minus 28C.

The day after Christmas was forecast to deliver lows of at least -20C through a wide swath, from Edmonton in the west to Quebec in the east.

Forecast to Persist For Days to Come

This harsh winter weather is expected to continue into the new year. There are warnings of possible electrical grid strain in Yukon territory in the coming days, as the territory’s power grid comes under strain from record-high energy demand.

The lengthy cold snap originates from the Arctic vortex settling above Canadian territory through December, allowing bitter Arctic air to spill south. The frigid dome is projected to gradually withdraw north gradually, enabling milder Pacific air to move across the US and into parts of southern Canada.

Stark Contrast with US Warmth

In stark contrast, parts of the US experienced their warmest Christmas Day on record 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.

Several states set Christmas Day temperature records. The capital of Oklahoma soared to 25C on Christmas Day, exceeding the old record of 22C from 1982. Urban centers like Austin, Dallas, and Charlotte, North Carolina similarly saw thermometers rise past the 25C mark.

Heat-Dome Effect Fuels Warmth

Unseasonable heat is predicted to persist through Boxing Day and the days ahead, with abnormal warmth projected to move into the south-eastern states later in the week.

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. As air sinks through the atmosphere, it compresses and heats further, enabling abnormally high temperatures to develop.