North Carolina Gov. Roy Cooper confirmed at least five storm-related deaths, and warned people who fled their homes against going back too soon.
More than 80,000 people were already without power as the storm began buffeting the coast, and more than 12,000 were in shelters.
"Life-threatening, catastrophic flash floods and prolonged significant river flooding are likely over portions of the Carolinas and the southern to central Appalachians from western North Carolina into southwest Virginia through early next week".
More than 60 people had to be pulled from a collapsing cinderblock motel.
Officials in North Myrtle Beach, where some flooding was occurring, did report some delays in their 911 emergency system, according to a news release, but their public safety personnel are still out in the community.
Other areas throughout the region reported flooded and impassable roads, downed trees and power lines and power outages of more than 125,000 customers. As of Saturday afternoon, about 752,000 homes and businesses were without power in North Carolina, along with 119,000 in SC. A 78-year-old man was electrocuted attempting to connect extension cords while another man perished when he was blown down by high winds while checking on his hunting dogs, a county spokesman said.
Shaken after seeing waves crashing on the Neuse River just outside his house in New Bern, restaurant owner and hurricane veteran Tom Ballance wished he had evacuated.
"The shelves are pretty empty, and we don't expect our first truck until Sunday, maybe, if they can get through", she said.
Florence made landfall 10 miles east of Wrightsville Beach, North Carolina, on Friday morning as a Category 1 hurricane with 90 mph winds. But Florence, a Category 1 when it hit, already had pounded coastal areas for hours.
The dead included a mother and baby killed when a tree fell on a house in Wilmington, North Carolina.
By Saturday morning the winds weakened to 50mph but the storm's slow speed means that communities in North Carolina are receiving a prolonged battering by torrential rain.
"The wind was so hard, the waters were so hard that, trying to get out, we got thrown into trailers". The southeast town of Newport, N.C., reported a rainfall total of nearly 24 inches as of midnight Saturday.
The rest of SC into western North Carolina and southwest Virginia is expected to report 5 to 10 inches of additional rainfall, with isolated cases of 15 inches.
The storm made landfall on Friday near Wilmington, a city of about 120,000 squeezed between North Carolina's Atlantic coastline and the Cape Fear River. CORRECTING GRAMMAR AND TYPO IN CITY NAME A family is stalled in water as they wait to be rescued during the passing of Hurricane Florence in the town of New Bern, North Carolina, U.S., September 14, 2018.
It's part of the same pattern that unfolded during Hurricane Katrina, when some 150,000 to 200,000 people remained in their homes despite federal evacuation orders, and during Hurricane Maria, which an independent study conducted by George Washington University recently revealed resulted in almost 3,000 deaths.
"You can walk faster than this storm is moving", said Wilmington Mayor Bill Saffo.
North Carolina alone is forecast to get 9.6 trillion gallons, enough to cover the Tar Heel state to a depth of about 10 inches.
Protected: More than 20,000 people in shelters in North Carolina, 6,400 in SC and 400 in Virginia.