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An intense cold spell has seized a bitter and extended period of frigid weather, with readings persisting in the minus 20 to minus 40 Celsius range for multiple 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

Similarly, the communities of Mayo and Dawson experienced over two straight weeks of nights below -40C, with the temperature in Mayo bottoming out at -50.4 degrees Celsius at the start of the week. The capital, Whitehorse, likewise saw a series of ten nights when readings fell to minus 30 degrees or lower.

The deep freeze spread farther south during the holiday season. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

December 26th was anticipated to usher in lows of at least -20C across many regions, encompassing cities from Edmonton to Quebec.

Forecast to Persist Through Early January

The frigid conditions are predicted to linger into the new year. Authorities have cautioned about potential power failures in the Yukon over the next several days, as the system endures record-high pressure from record-high energy demand.

This extended freeze is the result of a stationary polar vortex over Canada for much of December, allowing bitter Arctic air to spill south. Next week, the cold air mass is expected to retreat north allowing more temperate air from the Pacific to sweep across America and reach into portions of southern Canada.

Stark Contrast to American Heat

Meanwhile, in a dramatic contrast, areas of the United States saw historically high temperatures for Christmas as readings skyrocketed 15 to 30 degrees Celsius above normal. For numerous locations, the weather resembled a spring day in April or May instead of the heart of winter.

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. Urban centers like Austin, Dallas, and Charlotte, North Carolina also logged readings above 25 degrees Celsius.

Heat-Dome Effect Fuels Warmth

Unseasonable heat is predicted to persist on December 26th and into the weekend, with abnormal warmth projected to move across the southeastern US in the coming days.

The warmth has been fuelled by a powerful high-altitude 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. Descending air compresses and adiabatically warms, allowing unusually warm temperatures to build.