Deep Freeze Grips Canada as America Sees Most Unseasonably Mild Christmas Ever.

A prolonged deep freeze has enveloped a severe and lengthy Arctic outbreak, with readings persisting between -20C and -40C for an extended duration. On Tuesday, Braeburn in the Yukon recorded -55.7C, its coldest December temperature in nearly five decades.

Prolonged Freeze of Extreme Cold

Meanwhile, Mayo and Dawson endured 16 consecutive nights colder than minus 40 degrees, with Mayo experiencing a low of -50.4C at the start of the week. Whitehorse also recorded a series of ten nights when the cold dipped under -30 Celsius.

This Arctic air mass pushed further southward during the holiday season. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

Boxing Day was expected to bring readings no higher than -20 Celsius across many regions, including Edmonton, Montreal, Ottawa and Quebec.

Expected to Continue Through Early January

The severe cold is forecast to persist into the new year. 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.

The lengthy cold snap originates from a stationary polar vortex above Canadian territory through December, enabling a surge of icy Arctic winds to descend. Next week, the cold air mass is expected to retreat north slowly, permitting warmer Pacific winds to flow over America and reach into portions of southern Canada.

Dramatic Difference to American Heat

Conversely, sections of America recorded the hottest December 25th in their history as the mercury climbed roughly 15 to 30 degrees above typical averages. Across wide regions, the atmosphere was more akin to late spring rather than the end of December.

Several states set Christmas Day temperature records. 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 also logged readings above 25 degrees Celsius.

Heat-Dome Effect Sustains High Temperatures

Above-average warmth is expected to continue through Boxing Day and the days ahead, with atypical high temperatures expected to spread across the southeastern US in the coming days.

The unseasonable temperatures are powered by a robust atmospheric 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 over a large portion of North America, trapping warm air near the surface. As air sinks through the atmosphere, it compresses and heats further, enabling abnormally high temperatures to develop.