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Northern Canada has been gripped by an intense and prolonged cold spell, with thermometers lingering from 20 to 40 degrees below zero for weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, its coldest December temperature in nearly five decades.

Prolonged Freeze of Extreme Cold

Meanwhile, Mayo and Dawson endured 16 consecutive nights dipping under the minus 40 Celsius threshold, with Mayo experiencing a low of -50.4C earlier this week. The capital, Whitehorse, likewise saw a series of ten nights when the cold dipped under -30 Celsius.

The deep freeze spread farther south over the festive period. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

The day after Christmas was forecast to deliver lows of at least -20C across many regions, including Edmonton, Montreal, Ottawa and Quebec.

Likely to Linger into the New Year

This harsh winter weather is expected to continue into the new year. Authorities have cautioned about potential power failures in the Yukon over the next several days, as the territory’s power grid comes under strain from record-high energy demand.

This extended freeze is the result of a stationary polar vortex above Canadian territory through December, allowing bitter Arctic air to spill south. In the coming week, forecasts indicate this cold air will pull back northward gradually, enabling milder Pacific air to move across America and reach into portions of southern Canada.

Stark Contrast Compared to Stateside Temperatures

Conversely, sections of America recorded their warmest Christmas Day on record as readings skyrocketed 15 to 30 degrees Celsius above normal. In many areas, conditions felt more typical of April or May than late December.

Several states set Christmas Day temperature records. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, 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

Warmer-than-normal conditions are forecast to last for the remainder of the week and beyond, with unseasonable heat forecast to sweep across the southeastern US in the coming days.

The warmth has been fuelled by a robust atmospheric 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 over a large portion of North America, effectively capping warm air at lower altitudes. Sinking atmospheric air undergoes compression and additional heating, enabling abnormally high temperatures to develop.