In its latest 1 pm BST update, the National Hurricane Center (NHC) said: "Radar data continue to indicate that the maximum sustained winds remain near 50 miles per hour (80 km/h) with higher gusts in heavy rainbands over water".
Florence maximum sustained winds are now down to 45 miles per hour.
After coming ashore in North Carolina as a Category 1 hurricane, Florence downgraded to a tropical storm on Friday afternoon and trudged into SC later in the night, reports CNN. Rainfall of up to 20 to 40 inches could fall over the next five days in some areas, forecasters say.
Forecasters say Florence is now a tropical storm but will continue to threaten North and SC with powerful winds and catastrophic freshwater flooding.
This remains a long duration event of flooding rain, storm surge and very strong winds over a widespread area.
Over 1,400 flights have been cancelled, according to FlightAware.com, as most of the coastal region's airports are closed to ride out the storm.
"Rivers are rising to risky levels, and the relentless rains will continue through the weekend", North Carolina Gov. Roy Cooper warned on Friday.
Top sustained winds are now about 100 km/h and the storm is moving to the west-southwest at 7 km/h - a track that is expected to continue through early Saturday.
Parts of North Carolina could see enough torrential rain to qualify as a thousand-year flood, said North Carolina Gov. Roy Cooper.
Neighbour Adam Sparks said he noticed emergency responders arrive at the house across the street right around when his power went out and the storm was intensifying.
With tropical storm-force winds swirling 350 miles wide, Florence continued deluging the Carolinas on Saturday morning after pushing surging seas far ashore.
US power companies said more than 974,000 homes and businesses, mostly in North Carolina and SC, were without power on Saturday after Florence hit the Southeast coast. Over 1 million people are under evacuation warnings, with 10 million more under storm watches and warnings, CBS News reports.
Florence flattened trees, buckled buildings and crumpled roads. Duke Energy provides power to 4 million people across the Carolinas.
"A big worry about Hurricane Florence is that it's not acting like a normal hurricane", said Al Jazeera's Andy Gallacher, reporting from Wilmington, North Carolina. USA media later said a second man in Lenoir County died after heavy winds knocked him down as he tried to check on his dogs.
A gust of 169km/h was recorded at Wilmington airport, surpassing the power of Hurricane Fran two decades ago. Later Friday, a wind gust of 68 miles per hour was measured at a station in Wrightsville Beach, near Wilmington.
One resident, restaurant owner Tom Ballance, told the Associated Press he now thinks he should have evacuated.
Ominously, forecasters said the onslaught on the North Carolina-South Carolina coast would last for hours and hours because the hurricane had come nearly to a dead stop at just 3 mph (6 kph) as of midday. It came ashore along a mostly boarded-up, emptied-out stretch of coastline.
"Flash flooding will be extreme and flood waters will come up quickly and seemingly out of nowhere", the governor said earlier.
Authorities warned, too, of risks of mudslides and environmental disasters from floodwaters washing over industrial waste sites and hog farms.
Additional rainfall will exacerbate flooding conditions as heavy rain bands continue to move through North and SC. That's enough to fill the Chesapeake Bay or cover the entire state of Texas with almost 10 centimetres of water, he calculated.
"Residents should not let their guard down", North Carolina Emergency Management tweeted.
In Jacksonville, North Carolina, next to Camp Lejeune, firefighters and police fought wind and rain as they went door to door to pull more than 60 people out of the Triangle Motor Inn after the structure began to crumble and the roof started to collapse.
Some of the worst flooding was in New Bern, where authorities were enforcing a curfew.