Wilmington - Emergency crews rescued hundreds of stranded people on Friday as Hurricane Florence pounded the US East Coast with driving rain, howling winds and dangerous storm surge.
"The storm is wreaking havoc on our state," North Carolina Governor Roy Cooper said. "We're deeply concerned for whole communities which could be wiped away."
Some of the worst flooding from the monster storm was in the town of New Bern, North Carolina, where the Neuse River overflowed its banks, flooding streets and trapping many people in their homes.
"WE ARE COMING TO GET YOU. You may need to move up to the second story, or to your attic, but WE ARE COMING TO GET YOU," the New Bern authorities said on Twitter.
Governor Cooper said no fatalities had been reported yet but there have been "several hundred" rescue operations and "there are still some people they need to get to".
"Rescue workers are working in dangerous conditions that will only get worse today," he said.
Cooper said the Neuse River had seen storm surge as high as 10 feet (three meters) and the amount of rainfall was a "1 000-year event."
He said 20 000 people were being housed in shelters across the state.
Hurricane Florence made landfall as a Category 1 storm at 07:15 (11:15 GMT) in Wrightsville Beach, North Carolina, after stalking the Carolina coast for days.
At 11:00 (15:00 GMT), the storm was packing maximum sustained winds of 130km/h and moving west-southwest at six kilometres per hour.
The National Hurricane Center (NHC) described Florence as a "slow mover" and said it had the potential to dump historic amounts of rainfall on North and South Carolina, as much as one metre in some places.
"This is not the end of it," said Jeff Byard, associate administrator for response and recovery at the Federal Emergency Management Agency (FEMA).
He said "24 to 36 hours remain for significant threats" from heavy rain, storm surge and flooding.
In New Bern, where a curfew was in place, city authorities said at least 150 people were awaiting rescue.
Besides federal and state emergency crews, they were being helped by volunteers from the so-called "Cajun Navy" who also turned up in Houston during Hurricane Harvey to carry out water rescues.
In Wilmington, near where the eye of the hurricane touched down, trees and power lines were down and many windows had been broken. The streets were mostly deserted and some were blocked by fallen trees.
The city woke on Friday to the sound of exploding electrical transformers with strong gusts throwing street signs and other debris as well as water in all directions.
Ken Graham, the NHC's director, warned the slow pace of the storm exacerbated its danger even to areas outside its immediate path. "The longer you have this hurricane wind flow, the longer you push that water well inland," he said.
Governor Cooper said half a million customers in North Carolina were without power and it could take weeks for it to be fully restored.
The NHC said the greatest threats to life came from storm-surges while "catastrophic flash flooding and prolonged significant river flooding" was expected.
The NHC said hurricane-force winds extended outward 130km from the center of the storm and tropical storm-force winds extended nearly 315km out.
A tornado watch was also in effect for parts of North Carolina.
In Wilmington, Mason Tarr said he spent the night at a friend's house but didn't sleep well.
"And it's just a Category 1 hurricane," Tarr said. "I wonder how it would have been with a Category 4 or 5.
"Our house is on high ground so we're not worried about the flooding," he said. "But there are a lot of big trees around so we preferred to spend the night at a friends to be sure.
"We're out of power so we spent the first few hours of the day playing board games with candles," he said.
About 1.7 million people in North Carolina, South Carolina and Virginia are under voluntary or mandatory evacuation orders and millions of others live in areas likely to be affected by the storm.
A state of emergency has been declared in five coastal states - North Carolina, South Carolina, Georgia, Maryland and Virginia.