US inhabitants eager to travel across the country and beyond during the coming holidays have been warned that a massive winter storm could leave them homebound for the third Christmas in a row.

The National Weather Service (NWS) issued on Wednesday a set of national warnings, including a blizzard warning and a winter storm warning that could affect much of the coming Christmas weekend.

"This will not be your average cold front as temperatures could drop 20 or more degrees within a few hours," the NWS said, warning of "record-breaking frigid temperatures" on the Gulf Coast and eastern US by Friday.

Airlines also alluded to potential delays and cancelations, while the NWS warned car travelers of the danger of driving amid such extreme weather conditions.

How severe is the winter storm expected to be?

Forecasters are predicting heavy snow, ice, flooding and powerful winds from Thursday to Saturday throughout much of the US, from the Plains and the Midwest to the East Coast, setting the scene for the coldest Christmas in decades.

The NWS and other official bodies have warned of potential power outages as a result. People were asked to postpone travel when possible.

Wind chills approaching 70 degrees below zero Fahrenehit (minus 57 Celsius) could hit the country's northern-most regions, with heavy snow expected in Idaho, Montana and Wyoming, the NWS said.

The middle of the country, meanwhile, is expecting frigid wind.

A NWS alert for Washington DC also warned of a winter storm with expected snow accumulations of up to 4 to 7 inches (10 to 18 cm) on Thursday.

The service warned of power outages and tree damage due to ice, urging citizens to develop a plan to "protect you, your pets, livestock and other property that are sensitive to extreme cold conditions."

Meanwhile in Buffalo, New York, the NWS described the forecast storm as a "once-in-a-generation storm", warning of wind gusts of over 65 mph and wind chill as low as 10 to 20 degrees below zero Fahrenheit.

How will travel be affected?

Ahead of the storm warnings, the Transportation Security Administration had projected holiday travel volume comparable to pre-pandemic levels. Most travel was initially slated for Thursday, when the extreme cold is due to set in.

As per estimates by the American Automobile Association, over 112 million people were expected to travel at least 50 miles (80.4 kilometers) away from home between December 23 and January 2. Most of such travel was expected to take place by car.

Many Americans were eager to plan road trips to visit families, or even book flight tickets, after two Christmases largely defined by pandemic isolation rules.