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A prolonged deep freeze has enveloped a bitter and extended period of frigid weather, with thermometers lingering from 20 to 40 degrees below zero for an extended duration. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, marking its chilliest December reading since 1975.

Prolonged Freeze Below -40C

Meanwhile, Mayo and Dawson endured sixteen nights in a row colder than minus 40 degrees, with Mayo experiencing a low of -50.4C earlier this week. Whitehorse similarly reported ten separate nights when readings fell to minus 30 degrees or lower.

The deep freeze spread farther south through Christmas week. Christmas night saw Edmonton's temperatures plummet below minus 28C.

December 26th was anticipated to usher in readings no higher than -20 Celsius through a wide swath, from Edmonton in the west to Quebec in the east.

Forecast to Persist Through Early January

The frigid conditions are predicted to linger for the foreseeable future. Authorities have cautioned about potential power failures in the Yukon in the coming days, as the territory’s power grid comes under strain from peak power usage levels.

This extended freeze is the result of a stationary polar vortex over Canada for much of 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 United States and penetrate southern Canadian regions.

Stark Contrast with US Warmth

Conversely, sections of America recorded the hottest December 25th in their history 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 instead of the heart of winter.

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 were also among those that recorded temperatures above 25C.

Atmospheric Ridge Sustains High Temperatures

Above-average warmth is expected to continue through Boxing Day and the days ahead, with unseasonable heat forecast to sweep into the south-eastern states later in the week.

The warmth has been fuelled by a strong upper-level ridge extending from the desert south-west towards the north and east, which generates a heat-dome phenomenon. This setup creates an extensive zone of high atmospheric pressure over a large portion of North America, effectively capping warm air at lower altitudes. Sinking atmospheric air undergoes compression and additional heating, allowing unusually warm temperatures to build.