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A prolonged deep freeze has enveloped a severe and lengthy Arctic outbreak, with temperatures hovering from 20 to 40 degrees below zero for weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, representing its most frigid December day since 1975.

Enduring Chill of Extreme Cold

Meanwhile, Mayo and Dawson endured over two straight weeks of nights below -40C, with Mayo plunging to -50.4C on Monday. Whitehorse similarly reported 10 nights when temperatures dropped below -30C.

This Arctic air mass pushed further southward over the festive period. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

The day after Christmas was forecast to deliver lows of at least -20C across many regions, from Edmonton in the west to Quebec in the east.

Likely to Linger into the New Year

This harsh winter weather is expected to continue into the new year. Authorities have cautioned about potential power failures in the Yukon soon, as the system endures record-high pressure from record-high energy demand.

This extended freeze is the result of the Arctic vortex settling above Canadian territory through December, allowing bitter Arctic air to spill south. Next week, the cold air mass is expected to retreat north slowly, permitting warmer Pacific winds to flow over the US and into parts of southern Canada.

Dramatic Difference Compared to Stateside Temperatures

In stark contrast, parts of the US experienced their warmest Christmas Day on record as temperatures soared about 15-30C above the seasonal average. For numerous locations, the weather resembled a spring day in April or May instead of the heart of winter.

A number of states broke historical records for December 25th warmth. The capital of Oklahoma soared to 25C on Christmas Day, surpassing the previous peak of 22C set in 1982. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina were also among those that recorded temperatures above 25C.

Atmospheric Ridge 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 across the southeastern US in the coming days.

The warmth has been fuelled by a strong upper-level ridge reaching from the arid southwest across the continent, which generates a heat-dome phenomenon. Such a configuration results in a widespread high-pressure system blanketing a significant part of the landmass, trapping warm air near the surface. Descending air compresses and adiabatically warms, allowing unusually warm temperatures to build.