Emergency workers went door to door urging people to flee Florence's rising waters and used inflatable boats to rescue others as the storm practically parked itself over land and poured on the rain today.
A day after Florence blew ashore in North Carolina with 144km/h winds, the death toll from the hurricane-turned-tropical storm sits at least five.
More than 600mm rain had fallen in places as the drenching went on and on, with forecasters saying there could be an additional 457mm by the end of the weekend.
Rivers and creeks rose toward historic levels, threatening flash flooding that could devastate communities and endanger dams, roads and bridges.
'I cannot overstate it: floodwaters are rising, and if you aren't watching for them you are risking your life,' North Carolina Governor Roy Cooper said.
In its initial onslaught along the coast, Florence buckled buildings, deluged entire communities and knocked out power to more than 870,000 homes and businesses.
But the storm was shaping up as a two-part disaster, with the second, delayed-action stage consisting of inland flooding, caused by rainwater working its way into rivers and streams.
The dead included a mother and baby killed when a tree fell on a house in Wilmington, North Carolina. South Carolina recorded its first death from the storm when officials said a 61-year-old woman was killed when her vehicle hit a tree that had fallen across a highway.
Officials in North Carolina's Harnett County, about 145km inland, urged residents of about 1100 homes to evacuate because the Lower Little River was rising toward record levels.
In New Bern, along the coast, aerial photos show homes completely surrounded by water, with rescuers using inflatable boats to reach people. More than 360 people have been carried to safety since Thursday night amid rising waters from a river swelled by both rain and salty storm surge.
A pet dog licked Johan Mackie's face after he helped rescue Kevin Knox's family from their flooded brick home. The Army sergeant was part of a team using a phone app to locate people in distress.
Mackie rode in a boat through a flooded neighborhood, navigating through trees and past a fence post to get to the Knox house.
'Amazing. They did awesome,' Kevin Knox said. Mr Knox was stranded with seven others, including a boy who was carried out in a life vest.
'If not we'd be stuck upstairs for the next ... how long? I have no idea.'
At 11am, Florence was centered about 65km west of Myrtle Beach, South Carolina, inching west at four km/h – not even as fast as a person can walk. Its winds were down to 75km/h.
With the eye of Florence stalled near the coast, the half of the storm still out over the Atlantic continued to collect warm ocean water and dump it on land.
Stream gauges across the region showed water levels steadily rising, with forecasts calling for rivers to crest Sunday and Monday at or near record levels.
The Little River, the Cape Fear, the Lumber, the Neuse, the Waccamaw and the Pee Dee were all projected to rise over their banks, flooding cities and towns.
Along the Lumber River in Lumberton, workers used heavy machinery to dump extra sand on a railbed prone to flooding.
National Hurricane Center Director Ken Graham said radar and rain gauges indicated some areas got as much as 762mm of rain, which he called 'absolutely staggering'.
'And we're not done yet,' Mr Graham said, adding that some hard-hit areas could get an additional 381 to 508mm because the storm was moving so slowly.