'Absolute coldest' deadly deep freeze grips Midwestern U.S., blamed for 12 deaths

CHICAGO, Jan 30 (Reuters) - A large swath of the United States was gripped by brutal cold and wind chills on Wednesday as record-low temperatures caused by a blast of Arctic air moved across the Midwest and into Eastern states, prompting residents to stay indoors.

Classes were canceled Wednesday and Thursday in Chicago, home of the nation's third-largest school system, and police warned of the risk of accidents on icy highways. The U.S. Postal Service temporarily set aside its credo about carrying mail regardless of "snow nor rain ... nor gloom of night," and halted deliveries from parts of the Dakotas through Ohio.

Temperatures in parts of the Northern Plains and Great Lakes plunged to as low minus 42 Fahrenheit (minus 41 Celsius) in Park Rapids, Minnesota, and minus 31F in Fargo, North Dakota, according to the National Weather Service.

Andrew Orrison, a meteorologist with the service, said the some of the coldest wind chills were recorded in International Falls, Minnesota, at minus 55F (minus 48C). That's significantly more frigid than an expected low of minus 28F (-33C) with wind chill in Antarctica.

"Really today is going to be the absolute coldest across the Northern Plains and across the Midwest... stretching down into the Ohio Valley as well," Orrison said in a phone interview on Wednesday. "Moving forward here, we are going to see a decent amount of this cold air move through the East Coast."

The bitter cold is being carried by the polar vortex, a stream of air that spins around the stratosphere over the North Pole, but whose current has been disrupted and is now pushing south.

TREACHEROUS DRIVING CONDITIONS

An Illinois police department found a fictitious cause for the icy blast, posting on Facebook that its officers had arrested Elsa, the frosty character from the Disney movie "Frozen," for bringing the arctic air to the Midwest.

The McLean Police Department shared a staged photo of officers putting a woman dressed in a blue princess gown in pink handcuffs and escorting her into a police car.

With officials in Midwest and the Northern states advising residents to stay indoors, dashcam footage from one trucker taken outside Grand Rapids, Michigan gave a snapshot of hair-raising driving conditions.

"I about just got caught in a giant wreck; cars are into other pickups, there's people hurt. I gotta let you go," Jason Coffelt is heard saying in an Instagram post on Tuesday, as his truck is forced off the highway and pulls up just before a multi-vehicle accident.

At least five deaths relating to cold weather were reported since Saturday in Iowa, Indiana, Illinois, Wisconsin and Minnesota, local media reports said.

More than 2,000 flights were canceled early on Wednesday, largely out of Chicago O'Hare and Chicago Midway international airports, the flight tracking site FlightAware.

Train service Amtrak said it would cancel all trains in and out of Chicago on Wednesday.

Most federal government offices in Washington D.C. opened three hours late on Wednesday due to the frigid weather already impacting the area.

(Reporting by Suzannah Gonzales, additional reporting by Rich McKay in Atlanta and Gina Cherelus in New York; Editing by Scott Malone and Bernadette Baum)