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Northern Canada has been gripped by a severe and lengthy Arctic outbreak, with temperatures hovering between -20C and -40C for multiple weeks. On Tuesday, Braeburn in the Yukon recorded -55.7C, its coldest December temperature in half a century.

Prolonged Freeze in the Deep Minus Forties

In addition, the locales of Mayo and Dawson suffered through 16 consecutive nights colder than minus 40 degrees, with Mayo plunging to -50.4C at the start of the week. Whitehorse also recorded 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.

The day after Christmas was forecast to deliver readings no higher than -20 Celsius through a wide swath, including Edmonton, Montreal, Ottawa and Quebec.

Likely to Linger For Days to Come

The severe cold is forecast to persist through the start of January. There are warnings of possible electrical grid strain in Yukon territory over the next several days, as the territory’s power grid comes under strain from peak power usage levels.

The prolonged chill has been caused by the polar vortex remaining anchored 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 slowly, permitting warmer Pacific winds to flow over 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. In many areas, conditions felt more typical of 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, exceeding the old record of 22C from 1982. Metropolitan areas such as Austin, Dallas, and Charlotte also logged readings above 25 degrees Celsius.

Atmospheric Ridge Drives the Heat

Unseasonable heat is predicted to persist on December 26th and into the weekend, with atypical high temperatures expected to spread into the south-eastern states later in the week.

The unseasonable temperatures are powered by a robust atmospheric ridge extending from the desert south-west towards the north and east, creating a heat-dome effect. Such a configuration results in a widespread high-pressure system across much of the continent, trapping warm air near the surface. As air sinks through the atmosphere, it compresses and heats further, enabling abnormally high temperatures to develop.