More than 200 million people were under an advisory or warning in the United States on Friday, according to the US National Weather Service (NWS).

The United States has been grappling with a severe winter storm that has led to the cancellation of thousands of flights during the holiday season.

What's the latest?

A pileup involving around 50 cars on an Ohio highway has killed at least two motorists, injured numerous others and shut down both lanes of the highway, state police officials said.

Stranded motorists on the Ohio Turnpike were evacuated by bus to keep them from freezing in their cars in sub-zero temperatures, according to the Toledo Fire & Rescue Department. The crashes happened near the city of Toledo.

In neighboring Kentucky, at least three people — two in car accidents and one who was homeless — died because of harsh weather.

"Please stay home and stay safe," Kentucky Governor Andy Beshear wrote on Twitter. He added thousands of home were also without power.

What did forecasters say about the storm?

The NWS's map "depicts one of the greatest extents of winter weather warnings and advisories ever," forecasters said.

Meteorologists said that it was so cold in some areas that anyone going outside could risk frostbite within minutes.

"When it's this cold, anybody can run into trouble," NWS forecaster Rich Maliawco told the Agence France-Presse (AFP) news agency.

"With these kinds of wind chills, if you're not wearing those warm layers ... unprotected skin can get frostbite in less than five minutes," he said.

Widespread power outages and travel disruptions

Around 1.4 million people, mainly in the south and east of the country, were without power as of Friday morning, according to poweroutage.us.

Hundreds of people in Georgia, including in capital city Atlanta, were without power Friday and facing the possibility of sub-zero wind chills without heat.

Two traffic fatalities were reported in Oklahoma on Thursday, while in Kansas three people died in road accidents, according to the state's highway patrol.

One hundred million people were expected to take to the roads, the American Automobile Association said.

The major northern I-90 highway was shut in South Dakota. Officials said it would not reopen until later Friday.

More than 3,250 flights were canceled on Friday, and another 1,900 were delayed, according to tracking website Flight Aware.

Transportation Secretary Pete Buttigieg warned that holiday travel was being severely affected by the storm. "To say we have the opposite of cooperative weather would be an understatement," he told the broadcaster MSNBC, adding that 10% of US commercial flights had been canceled on Thursday.