As of Friday afternoon the storm had already claimed four lives, including a mother and her baby who were killed when a tree fell on their house in Wilmington, North Carolina. The father was hospitalized with injuries.
Nearly 800,000 people are reported to be without power already in North Carolina, and officials have warned restoring electricity could take days or even weeks.
Two men in their 70s were killed in Lenoir County. It's believed he died after he was blown down while going outside to check on his dogs.
North Carolina Gov. Roy Cooper called Florence an "uninvited brute" that could wipe out entire communities as it grinds across the state. The destination for the crews is Camp McCrady, a National Guard training center in SC. Officials have not said how the fire started, but attributed it to the storm.
A day after blowing ashore with 90 miles per hour (145 kph) winds, Florence practically parked itself over land all day long and poured on the rain. According to the South Carolina Department of Public Safety, a pick-up truck drove into standing water on the road and lost control, overturning into a ditch.
"It can not be emphasized enough that the most serious hazard associated with slow-moving Florence is extremely heavy rainfall, which will cause disastrous flooding that will be spreading inland through the weekend", the National Hurricane Center said in an advisory at 5 a.m. Friday.
Hundreds of thousands were without power in the Carolinas late Friday.
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.
Protected: 12,000 people in shelters in North Carolina, 6,400 in SC and 400 in Virginia. A nuclear power plant in Brunswick, NC, has shut operations.
Also of concern is the sprawling Norfolk Naval Shipyard in Virginia and Marine Corps bases at Camp Lejeune and Cherry Point in North Carolina and at Parris Island in SC. But once New Bern TV news station WCTI evacuated its newsroom Thursday night because of flooding and people began to lose power, the seriousness of the situation began dawning on folks, she said.
One city in North Carolina has picked up more than 23 inches (58 centimetres) of rain in two days.More news: U.S., Canada slug it out as deadline looms to clinch NAFTA
SC authorities reported one death. "We are deeply concerned about the inland flooding".
"I can not overstate it: Floodwaters are rising, and if you aren't watching for them, you are risking your life", Gov. Roy Cooper said.
"There is going to be a lot of rain".
Maluyo said local and national governments have been preparing for the storm since Monday, with school and offices closing down.
Forecasters warned rainfall of up to 40 inches could hit the land, triggering flash floods. The rainfall will produce life-threatening flash flooding. Almost 2,100 flights have been canceled through Saturday.
According to the U.S. National Weather Service, there are 5.25 million residents in areas under hurricane warnings or watches, and 4.9 million in places under tropical storm warnings or watches.
Washington, DC, Mayor Muriel Bowser and the governors of North Carolina, South Carolina, Virginia, Georgia and Maryland declared states of emergency.
President Donald Trump praised the "incredible job" being done by the Federal Emergency Management Agency workers and first-responders.
Still big: tropical-force winds extending out up to 175 miles from the center.
Storm surges - the bulge of ocean water pushed ashore by the hurricane - were as high as three metres.
Those waves were coming from the Neuse River, which is about 25 feet (8 meters) away, and downhill, from his house.