Hurricane Matthew's rains are triggering severe flooding in North Carolina as the deteriorating storm made its exit to the sea, and thousands of people had to be rescued from their homes and cars.
The death toll in the US climbed to at least 14, half of them in North Carolina.
The storm was stripped of hurricane status just before daybreak.
"As the sun rises in North Carolina and the blue sky returns, our state is facing major destruction and, sadly, loss of life,'' Governor Pat McCrory said as the effects of Saturday's deluge became clearer at daylight.
Governor McCrory said police and emergency crews had made more than 880 water rescues.
In the Fayetteville alone, emergency workers and police saved nearly 600 people from rapidly rising floodwaters, officials said.
The governor said four people were missing in the Fayetteville area, and that the full scale of the disaster was not yet known because the flooding continued overnight and there were many places that search teams had not yet reached.
Most of the deaths happened when vehicles were swept away by floodwaters.
Forecasters said North Carolina and Virginia could get even more rain and warned of the danger of life-threatening flooding through Monday night.
It came as a weakened Hurricane Matthew has made landfall in South Carolina yesterday.
In Haiti, where Matthew was a monster Category 4 when it slammed into the poorest country in the western hemisphere on Tuesday, the official death toll rose to at least 336. It is believed the actual figure is closer to 900, with a Reuters count putting the number dead at 877.
An updated official toll may not be announced until Wednesday.
At least nine were killed in the United States, with reports of two more dead.
The interim president of Haiti, Jocelerme Privert, has announced three days of national mourning,which began yesterday.
The scope of the devastation in the south of the Caribbean country was becoming clearer but the toll remains provisional due to the difficulty of gaining access to some areas.
Half a million children live in the worst-hit departments in southern Haiti, according to UNICEF, which said it needed at least $5 million to meet their immediate needs.
Pledges of aid have flooded in, with the United States announcing it was sending the USS Mesa Verde, whose 300 Marines will add to the 250 personnel and nine helicopters already ordered to deploy to Haiti.
France announced it was sending 60 troops, with 32 tonnes of humanitarian supplies and water purification equipment.
California-based charity International Relief Teams said it was donating US$7 million in medical supplies with international organizations MAP International and Hope for Haiti.
Other places south of the Carolinas, meanwhile, began getting back to normal, with millions relieved that the storm wasn't the catastrophe that many had been bracing for.
With AFP.