Photos: Historic winter blast batters US ahead of holiday travel rush

A person in downtown Milwaukee as a winter storm moves through much of the United States. At least 4,200 flights were cancelled ahead of the country's busiest travel weekend of the year as an Arctic cold front slices through the Lower 48.

A crew from A's Auto and Truck Repair in Guilford helps clean up one of the two three-vehicle crashes along Route 30 in Jamaica, Vt., during a snowstorm. A monstrous, once-in-a-decade winter storm is battering the US, bringing heavy snow, searing winds and dangerously low temperatures while causing mayhem for travellers across the country at the peak of the holiday season.

Travellers wait through security at San Francisco International Airport (SFO) in San Francisco, California, US. According to AAA, a travel insurance provider, an estimated 112.7 million people will travel 50 miles or more from Dec. 23 to Jan. 2, up by 3.6 million from last year and getting close to pre-pandemic levels.

Ice is removed from a United Airlines jet after a cold weather front moved into General Mitchell International Airport in Milwaukee, Wisconsin, U.S. As of early Friday, more than 200 million people "- around 60% of the nation's population "- were under some form of winter weather warning or advisory, according to the National Weather Service. Snow is set to blanket the Great Lakes region and parts of northern New York state and New England.

"This is not like a snow day; you know when you're a kid. This is serious stuff," President Joe Biden said in a briefing, calling it "dangerous" and threatening. "If you all have travel plans, leave now. Not a joke." Above, drivers navigate a snow-covered street as temperatures hang in the single digits in Chicago, Illinois.

Commuters navigate a snow-covered Kennedy Expressway during a lighter-than-usual evening rush hour as temperatures hang in the single digits in Chicago, Illinois.

Brianna Brooks, owner of Scott Brooks Towing out of Townshend, Vt., hooks up a vehicle to a flatbed truck at a three-vehicle crash site during a snowstorm .

Travellers arrive for flights at O'Hare International Airport in Chicago, Illinois. A winter weather system bringing snow, high winds, and sub-zero temperatures has wreaked havoc on airlines' holiday travel during one of the busiest days of the year.

Semitrucks line up in the eastbound land on I-70, which was closed due to extreme winter driving conditons, in Silverthorne, Colorado.

Passengers queue up to go through security at Detroit Metro Airport in Romulus, Michigan.

Rows of headstones at the North Dakota Veterans Cemetery are blanketed by drifting snow in Mandan, N.D.