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Temperatures overnight sank into the negative double digits in nearly a dozen states, with the polar vortex descending on the Midwest and threatening to break all-time cold records.

The big picture: Mail deliveries have been suspended, schools and businesses closed, and Midwesterners warned that the frigid cold is not to be trifled with. Even so, some brave souls have ventured outside to test out the temperatures.

A bicyclist in southwest Minneapolis in below-freezing temperatures. Photo: Kerem Yucel/AFP via Getty Images

Steam rising from the Chicago river because the air is so cold. 

Steam rises above the North Branch Chicago River as temperatures dropped to minus 22°F. Photo: Joshua Lott/AFP via Getty Images

Polar vortex to set painful all-time records

USPS suspends delivery in 11 states, citing safety concerns

Polar vortex preys on the Midwest with coldest air in a generation

In photos: Boiling water freezes, train tracks lit on fire in severe cold

The frigid temperatures are not to be trifled with.

Etrade sign that shows the temperature as minus 21 degrees 

In New York City on Wednesday. Photo: Scott Olson via Getty Images

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Polar Vortex

Extreme weather

Temperatures overnight sank into the negative double digits in nearly a dozen states, with the polar vortex descending on the Midwest and threatening to break all-time cold records.The big picture: Mail deliveries have been suspended, schools and businesses closed, and Midwesterners warned that the frigid cold is not to be trifled with. Even so, some brave souls have ventured outside to test out the temperatures.

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In photos: Boiling water freezes, train tracks lit on fire in severe cold

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