Some towns have already had more than 60-centimetres of rain, and forecasters warn that totals could hit one-metre.
"Many people who think that the storm has missed them have yet to see its threat", North Carolina Gov. Roy Cooper said. Officials said some 1.7 million people in the Carolinas and Virginia were warned to evacuate, but it was unclear how many did.
The city of about 29,000, which was founded in the early 1700s, is near the North Carolina coast and is bordered on the east and south, respectively, by two rivers.
On the other side of the world, meanwhile, more than a dozen people have died as Typhoon Mangkhut rips through the Philippines.
After looking at an analysis of expected rainfall, flooding and the effects of Hurricane Matthew, which hit SC as a Category 1 storm in 2016, officials determined that the Pee Dee River basin could flood, swelling rivers that would overtake a number of bridges on major routes, as early as Monday night. A 78-year-old man connecting extension cords in the rain was electrocuted, according to Roger Dail, the Lenoir County director of emergency services. The price tag on the rebuild efforts for areas devastated by storm surge, which was expected to reach as high as 20 feet in some areas, was still impossible to quantify.
The Philippines tends to get hit almost every year, the Carolinas far less frequently though with lots of close calls, Maue said.
Florence is moving slowly across eastern SC, and according to the National Hurricane Center is producing "catastrophic flooding over North and SC". But Florence, a Category 1 when it hit, already had pounded coastal areas for hours.
A mother and infant were killed in Wilmington, North Carolina, when a tree fell on their home.
While Florence is, as of 12:00 p.m. ET on Saturday, now "just" a tropical storm, it has still ripped the Carolina coast with heavy winds and record-breaking rainfall, causing widespread damage for humans and wildlife alike.
But it was clear that this was really about the water, not the wind.
More than 23 inches have fallen in some towns.
The Florence center is crawling inland over SC, but its main rain bands are hitting already-saturated North Carolina - setting up what may be days of flooding for some communities. Seventy people had to be pulled from a collapsing hotel at the height of the storm, and many more who defied evacuation orders were hoping to be rescued.
A man sits on a park bench in a flooded park as the Cape Fear River rises above its usual height in Wilmington, N.C., on Friday.
Members of the North Carolina National Guard finish stacking sand bags under a highway overpass near the Lumber River which is expected to flood from Hurricane Florence's rain in Lumberton, North Carolina, on September 14, 2018. The death not related to the hurricane and it is under investigation.
Yet a day after landfall the faster-moving Mangkhut was back out over open water - weakened, but headed across the South China Sea toward China.
Authorities fear the death toll will go higher as the tropical storm crawls westwards across SC. That's enough to fill the Chesapeake Bay or cover the entire state of Texas with almost 4 inches (10 centimeters) of water, he calculated.