The National Hurricane Centre said the storm “is producing a life-threatening storm surge”.

North Carolina Governor Roy Cooper told a news conference that the “historic” hurricane would unleash rains and floods that would inundate almost the entire state in metre or more of water.

National Weather Service forecaster Brandon Locklear said in a video briefing North Carolina would see the equivalent of up to eight months of rain in a two- to three-day period.

North Carolinians made last-minute preparations and hunkered down to await Florence’s arrival. A few hardy locals gathered at Cape Fear Wine and Beer pub in downtown Wilmington.

“We lost power at home so we figured we should come to the bar,” said Carla Mahaffee, a 33-year-old actor from Wilmington, as she drank a cider. “We’ve prepared all our supplies at home and frankly, we were bored.”

Holly Waters, a retired special education teacher from Wilmington, said she was happy to have a place to go to relax before the storm worsened.

“It’s not the middle of a hurricane yet, so why not come for a beer?” said Waters, 54.

Elsewhere in Wilmington, Linda Smith, a 67-year-old retired non-profit director, was concerned as she watched wind gusts stir up frothy white caps on the Cape Fear River.

“We’re a little worried about the storm surge so we came down to see what the river is doing now,” Smith said. “I am frightened about what’s coming. We just want prayers from everyone.”

At least 88,000 people were without power in North Carolina with the brunt of the storm yet to come, according to the state’s emergency management agency. Millions of people were expected to lose power from the storm and restoration could take weeks.

Roads and intersections on North Carolina’s Outer Banks barrier islands were already inundated with water.

Florence’s top winds were clocked on Thursday evening at 150km/h as it churned in the Atlantic Ocean, down from a peak of 225km/h earlier this week when it was classified a Category 4 storm.

The storm’s center was about 80km south of Morehead City at around 11pm EST.

About 10 million people could be affected by the storm and more than 1 million had been ordered to evacuate the coasts of the Carolinas and Virginia, jamming westbound roads and highways.

At least 12,000 people had taken refuge in 126 emergency shelters, Cooper said, with more facilities being opened.

The National Hurricane Centre warned the threat of tornadoes was increasing as Florence neared shore and South Carolina Governor Henry McMaster said the heavy rains could trigger landslides in the western part of his state.

NHC Director Ken Graham said on Facebook the storm surges could push in as far as 2 miles (3km). Heavy rains were forecast to extend into the Appalachian Mountains, affecting parts of Alabama, Tennessee, Kentucky and West Virginia.

Emergency declarations were in force in Georgia, South and North Carolina, Virginia, Maryland and the District of Columbia.

Despite pleas from officials, some residents rejected calls to evacuate.

Near the beach in Wilmington, a Waffle House restaurant, part of a chain with a reputation for staying open during disasters, had no plans to close, even if power was lost, and there were lines to get in on Thursday evening.

Will Epperson, a 36-year-old golf course assistant superintendent, said he and his wife had planned to ride out the storm at their home in Hampstead, North Carolina, but then reconsidered. Instead, they drove 240km inland to his mother’s house in Durham.

“I’ve never been one to leave for a storm but this one kind of had me spooked,” Epperson said.