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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 multiple weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, representing its most frigid December day since 1975.

Enduring Chill in the Deep Minus Forties

Meanwhile, Mayo and Dawson endured over two straight weeks of nights colder than minus 40 degrees, with Mayo experiencing a low of -50.4C at the start of the week. Whitehorse similarly reported 10 nights when readings fell to minus 30 degrees or lower.

The bitter chill extended its reach south during the holiday season. Christmas night saw Edmonton's temperatures plummet below minus 28C.

December 26th was anticipated to usher in lows of at least -20C through a wide swath, encompassing cities from Edmonton to Quebec.

Forecast to Persist For Days to Come

The severe cold is forecast to persist through the start of January. Authorities have cautioned about potential power failures in the Yukon over the next several days, as its energy infrastructure faces unprecedented demand from record-high energy demand.

The prolonged chill has been caused by the polar vortex remaining anchored over Canada for much of December, which funnels frigid northern air southward. Next week, the cold air mass is expected to retreat north slowly, permitting warmer Pacific winds to flow over the United States and penetrate southern Canadian regions.

Dramatic Difference with US Warmth

Conversely, sections of America recorded their warmest Christmas Day on record as the mercury climbed roughly 15 to 30 degrees above typical averages. For numerous locations, the weather resembled a spring day in April or May rather than the end of December.

A number of states broke historical records for December 25th warmth. In Oklahoma, Oklahoma City hit 25C on Tuesday, 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.

Atmospheric Ridge Drives the Heat

Above-average warmth is expected to continue on December 26th and into the weekend, with abnormal warmth projected to move across the southeastern US in the coming days.

This heat is being driven by a strong upper-level ridge extending from the desert south-west towards the north and east, establishing a classic heat-dome pattern. Such a configuration results in a widespread high-pressure system blanketing a significant part of the landmass, effectively capping warm air at lower altitudes. Sinking atmospheric air undergoes compression and additional heating, allowing unusually warm temperatures to build.