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A prolonged deep freeze has enveloped a bitter and extended period of frigid weather, with thermometers lingering in the minus 20 to minus 40 Celsius range for weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, representing its most frigid December day in half a century.

Enduring Chill Below -40C

Similarly, the communities of Mayo and Dawson experienced 16 consecutive nights colder than minus 40 degrees, with Mayo experiencing a low of -50.4C at the start of the week. The capital, Whitehorse, likewise saw a series of ten nights when the cold dipped under -30 Celsius.

The deep freeze spread farther south during the holiday season. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

December 26th was anticipated to usher in readings no higher than -20 Celsius across many regions, from Edmonton in the west to Quebec in the east.

Forecast to Persist For Days to Come

The frigid conditions are predicted to linger into the new year. There are warnings of possible electrical grid strain in Yukon territory soon, as the territory’s power grid comes under strain from peak power usage levels.

The prolonged chill has been caused by the Arctic vortex settling across the northern part of the continent this month, enabling a surge of icy Arctic winds to descend. In the coming week, forecasts indicate this cold air will pull back northward allowing more temperate air from the Pacific to sweep across the US and into parts of southern Canada.

Stark Contrast to American Heat

In stark contrast, parts of the US experienced the hottest December 25th in their history as readings skyrocketed 15 to 30 degrees Celsius above normal. Across wide regions, the atmosphere was more akin to late spring than late December.

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. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina similarly saw thermometers rise past the 25C mark.

Heat-Dome Effect Drives the Heat

Warmer-than-normal conditions are forecast to last for the remainder of the week and beyond, with atypical high temperatures expected to spread into the south-eastern states later in the week.

The unseasonable temperatures are powered by a strong upper-level ridge stretching from the southwestern deserts northward and eastward, which generates a heat-dome phenomenon. Such a configuration results in a widespread high-pressure system over a large portion of North America, which holds warm air close to the ground. Descending air compresses and adiabatically warms, fostering the buildup of exceptional warmth.