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An intense cold spell has seized an intense and prolonged cold spell, with thermometers lingering in the minus 20 to minus 40 Celsius range for weeks. On Tuesday, Braeburn in the Yukon recorded -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 below -40C, with Mayo experiencing a low of -50.4C at the start of the week. Whitehorse similarly reported a series of ten nights when readings fell to minus 30 degrees or lower.

The bitter chill extended its reach 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.

Forecast to Persist into the New Year

The severe cold is forecast to persist into the new year. Officials have warned that the Yukon could face electricity outages over the next several days, as its energy infrastructure faces unprecedented demand from peak power usage levels.

The prolonged chill has been caused by the polar vortex remaining anchored over Canada for much of December, 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 the US and into parts of southern Canada.

Stark Contrast with US Warmth

Conversely, sections of America recorded their warmest Christmas Day on record as temperatures soared about 15-30C above the seasonal average. Across wide regions, the atmosphere was more akin to late spring rather than the end of December.

A number of states broke historical records for December 25th warmth. 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 Drives the Heat

Unseasonable heat is predicted to persist 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 warmth has been fuelled by a powerful high-altitude ridge stretching from the southwestern deserts northward and eastward, creating a heat-dome effect. This pattern establishes a broad area of high pressure 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.