Arctic Blast Tightens Hold on Canada as US Records Warmest Christmas Ever.

Northern Canada has been gripped by a severe and lengthy Arctic outbreak, with thermometers lingering between -20C and -40C for multiple weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, representing its most frigid December day in half a century.

Enduring Chill of Extreme Cold

Similarly, the communities of Mayo and Dawson experienced 16 consecutive nights colder than minus 40 degrees, with the temperature in Mayo bottoming out at -50.4 degrees Celsius earlier this week. Whitehorse similarly reported 10 nights when the cold dipped under -30 Celsius.

This Arctic air mass pushed further southward over the festive period. 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, including Edmonton, Montreal, Ottawa and Quebec.

Likely to Linger Through Early January

This harsh winter weather is expected to continue 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 peak power usage levels.

The lengthy cold snap originates from a stationary polar vortex across the northern part of the continent this month, 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 the US and into parts of southern Canada.

Pronounced Disparity with US Warmth

In stark contrast, parts of the US experienced historically high temperatures for Christmas as readings skyrocketed 15 to 30 degrees Celsius above normal. Across wide regions, the atmosphere was more akin to late spring than late December.

Multiple states established new Christmas temperature highs. 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 were also among those that recorded temperatures above 25C.

Heat-Dome Effect Sustains High Temperatures

Above-average warmth is expected to continue on December 26th and into the weekend, with unseasonable heat forecast to sweep through the American Southeast soon.

The warmth has been fuelled by a powerful high-altitude ridge stretching from the southwestern deserts northward and eastward, establishing a classic heat-dome pattern. 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, enabling abnormally high temperatures to develop.