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A prolonged deep freeze has enveloped a bitter and extended period of frigid weather, with thermometers lingering between -20C and -40C for multiple weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, marking its chilliest December reading since 1975.

Enduring Chill Below -40C

Similarly, the communities of Mayo and Dawson experienced over two straight weeks of nights colder than minus 40 degrees, with Mayo experiencing a low of -50.4C on Monday. 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.

Boxing Day was expected to bring readings no higher than -20 Celsius 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. Officials have warned that the Yukon could face electricity outages in the coming days, as the system endures record-high pressure from record-high energy demand.

This extended freeze is the result of the polar vortex remaining anchored above Canadian territory through December, enabling a surge of icy Arctic winds to descend. Next week, the cold air mass is expected to retreat north allowing more temperate air from the Pacific to sweep across the US and into parts of southern Canada.

Dramatic Difference 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. In many areas, conditions felt more typical of April or May instead of the heart of winter.

Several states set Christmas Day temperature records. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, topping the prior high mark of 22 degrees established over forty years ago. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina were also among those that recorded temperatures above 25C.

High-Pressure System Fuels Warmth

Above-average warmth is expected to continue through Boxing Day and the days ahead, with unseasonable heat forecast to sweep into the south-eastern states later in the week.

The unseasonable temperatures are powered by a robust atmospheric ridge extending from the desert south-west towards the north and east, which generates a heat-dome phenomenon. This pattern establishes a broad area of high pressure across much of the continent, which holds warm air close to the ground. As air sinks through the atmosphere, it compresses and heats further, fostering the buildup of exceptional warmth.