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A prolonged deep freeze has enveloped an intense and prolonged cold spell, with temperatures hovering between -20C and -40C for multiple weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, its coldest December temperature in half a century.

Prolonged Freeze in the Deep Minus Forties

Similarly, the communities of Mayo and Dawson experienced 16 consecutive nights below -40C, with the temperature in Mayo bottoming out at -50.4 degrees Celsius at the start of the week. The capital, Whitehorse, likewise saw a series of ten nights when the cold dipped under -30 Celsius.

This Arctic air mass pushed further southward through Christmas week. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

Boxing Day was expected to bring minimum temperatures of at least minus 20C through a wide swath, encompassing cities from Edmonton to Quebec.

Likely to Linger Through Early January

This harsh winter weather is expected to continue for the foreseeable future. There are warnings of possible electrical grid strain in Yukon territory over the next several days, as its energy infrastructure faces unprecedented demand from historically high electricity consumption.

This extended freeze is the result of the Arctic vortex settling across the northern part of the continent this month, which funnels frigid northern air southward. The frigid dome is projected to gradually withdraw north gradually, enabling milder Pacific air to move across America and reach into portions of southern Canada.

Dramatic Difference to American Heat

Conversely, sections of America recorded their warmest Christmas Day on record as readings skyrocketed 15 to 30 degrees Celsius above normal. For numerous locations, the weather resembled a spring day in April or May instead of the heart of winter.

Multiple states established new Christmas temperature highs. The capital of Oklahoma soared to 25C on Christmas Day, 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.

Heat-Dome Effect Fuels Warmth

Warmer-than-normal conditions are forecast to last for the remainder of the week and beyond, with abnormal warmth projected to move into the south-eastern states later in the week.

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. This setup creates an extensive zone of high atmospheric pressure over a large portion of North America, trapping warm air near the surface. As air sinks through the atmosphere, it compresses and heats further, fostering the buildup of exceptional warmth.