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An intense cold spell has seized a severe and lengthy Arctic outbreak, with readings persisting between -20C and -40C for weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, representing its most frigid December day in half a century.

Consecutive Nights Below -40C

Meanwhile, Mayo and Dawson endured 16 consecutive nights colder than minus 40 degrees, with the temperature in Mayo bottoming out at -50.4 degrees Celsius on Monday. Whitehorse similarly reported 10 nights when readings fell to minus 30 degrees or lower.

The deep freeze spread farther south over the festive period. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

Boxing Day was expected to bring readings no higher than -20 Celsius in numerous areas, from Edmonton in the west to Quebec in the east.

Likely to Linger into the New Year

The severe cold is forecast to persist for the foreseeable future. Officials have warned that the Yukon could face electricity outages soon, as the system endures record-high pressure from peak power usage levels.

This extended freeze is the result of a stationary polar vortex across the northern part of the continent this month, enabling a surge of icy Arctic winds to descend. The frigid dome is projected to gradually withdraw north allowing more temperate air from the Pacific to sweep across America and reach into portions of southern Canada.

Stark Contrast with US Warmth

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. Across wide regions, the atmosphere was more akin to late spring instead of the heart of winter.

Multiple states established new Christmas temperature highs. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, exceeding the old record of 22C from 1982. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina similarly saw thermometers rise past the 25C mark.

Heat-Dome Effect Sustains High Temperatures

Warmer-than-normal conditions are forecast to last through Boxing Day and the days ahead, with atypical high temperatures expected to spread through the American Southeast soon.

The unseasonable temperatures are powered by a strong upper-level 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 blanketing a significant part of the landmass, trapping warm air near the surface. Sinking atmospheric air undergoes compression and additional heating, fostering the buildup of exceptional warmth.