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A prolonged deep freeze has enveloped a severe and lengthy Arctic outbreak, with temperatures hovering between -20C and -40C for weeks. On Tuesday, Braeburn in the Yukon recorded -55.7C, its coldest December temperature since 1975.

Enduring Chill Below -40C

In addition, the locales of Mayo and Dawson suffered through sixteen nights in a row colder than minus 40 degrees, with Mayo experiencing a low of -50.4C at the start of the week. Whitehorse similarly reported a series of ten nights when temperatures dropped below -30C.

This Arctic air mass pushed further southward over the festive period. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

The day after Christmas was forecast to deliver lows of at least -20C through a wide swath, including Edmonton, Montreal, Ottawa and Quebec.

Forecast to Persist 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 soon, as the system endures record-high pressure from record-high energy demand.

This extended freeze is the result of the Arctic vortex settling across the northern part of the continent this month, 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 United States and penetrate southern Canadian regions.

Stark Contrast to American Heat

Conversely, sections of America recorded historically high temperatures for Christmas as the mercury climbed roughly 15 to 30 degrees above typical averages. Across wide regions, the atmosphere was more akin to late spring instead of the heart of winter.

Several states set Christmas Day temperature records. 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.

Atmospheric Ridge Drives the Heat

Unseasonable heat is predicted to persist for the remainder of the week and beyond, with unseasonable heat forecast to sweep across the southeastern US in the coming days.

This heat is being driven by a powerful high-altitude ridge reaching from the arid southwest across the continent, 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, enabling abnormally high temperatures to develop.