"It's an uninvited brute who doesn't want to leave", said North Carolina Gov. Roy Cooper.
Parts of North and SC can expect an additional 10 to 15 inches.
Residents of New Bern, NC and their dog are rescued from rising floodwaters caused by Hurricane Florence.
Cooper said others should not follow suit.
"These are folks who chose to stay and ride out the storm for whatever reason, despite having a mandatory evacuation", city public information officer Colleen Roberts said.
"This system is unloading an epic amount of rainfall: in some places, measured in feet, not inches".More news: Turkish central bank hikes interest rates to 24%
Flooding from Hurricane Florence swept across the Carolinas early on Friday as the massive storm surged toward the coast, threatening record rainfall and leaving scores trapped by rising waters.
"Right now we've rescued over 400 people".
Resident Jay Manning said he and his wife watched with alarm as water filled the street.
The 18th century town, with a population of 30,000, has been badly flooded, with 4,200 homes damaged.
Forecasters say Florence is now a tropical storm but will continue to threaten North and SC with powerful winds and catastrophic freshwater flooding.
One of the towns worst affected is New Bern, which sits between the Neuse and Trent rivers in North Carolina.
A mother and infant were killed in Wilmington, N.C. after a tree fell on a house there while the Category 1 hurricane throttled the eastern North Carolina coastline Friday morning.More news: As Hurricane Florence Makes Landfall, Trump Tweets Support to First Responders
Evacuation zones in Horry and Georgetown counties remain under the order.
Downed trees reportedly blocked several roads in Richland and Lexington counties Saturday morning, including on Heathwood Circle in Columbia and Hayride Road in Gilbert.
United States media later said a man in Lenoir County died after heavy winds knocked him down as he tried to check on his dogs.
Hurricane Florence has barrelled into the Carolina coast and moved inland, knocking down trees, overflowing rivers, dumping sheets of rain and leading to the death of five people before it was downgraded to a tropical storm still capable of wreaking havoc.
On Friday, coastal streets in the Carolinas flowed with frothy ocean water, pieces of torn-apart buildings flew through the air, and at least 525,000 homes and businesses were without power, almost all of them in North Carolina.
The White House said Friday U.S. President Donald Trump will travel to areas hit by Hurricane Florence next week, once it has been determined that his travel would not disrupt any rescue or recovery efforts.
Florence peaked at a terrifying Category 4 with top winds of 140 mph (225 kph) over warm ocean water before making landfall as a Category 1 hurricane at 7:15 a.m.at Wrightsville Beach, a few miles (kilometers) east of Wilmington and not far from the SC line.More news: "No-deal" Brexit would complicate driving, data and roaming, United Kingdom says