A powerful blast of Arctic air is set to hit the United States starting November 26, bringing dangerous cold and snow during one of the busiest Thanksgiving travel weeks on record. The National Weather Service says the polar vortex may dip far south, sending below-normal temperatures across the Pacific Northwest, Great Plains, Midwest, and Mid-Atlantic.
Forecasters warn that the polar vortex, combined with the Madden–Julian Oscillation and La Niña, could create winter-like conditions through early December. Heavy snow is possible in the Central Rockies from November 29 to December 1, and in the Upper Great Lakes and Interior Northeast from November 29–30, with colder weather likely to linger into mid-December.
As millions prepare for a challenging holiday week, click through the following gallery to learn how the polar vortex triggers extreme wintry weather.