Myrtle Beach Online reported that some areas could see 20 to 30 inches of rain by the time the storm passes.
Early on Friday, South Carolina emergency officials said there was still time, "but not a lot of time" for people to leave flood-prone areas.
- Emergency workers went door to door urging people to flee Florence's rising floodwaters Saturday and rescuers used inflatable boats to pluck others from homes already submerged as the storm's epic deluge swelled rivers and creeks across the Carolinas. Florence was one of two major storms threatening millions of people on opposite sides of the world.
The now Category 1 storm's intensity diminished as it neared land, with winds dropping to 90 miles per hour (135 kph) by nightfall.
The National Hurricane Center said Florence will eventually make a right hook to the northeast over the southern Appalachians, moving into the mid-Atlantic states and New England as a tropical depression by the middle of next week.
Two people died in Lenoir County.
Charlotte and Asheville in North Carolina, and Roanoke, Virginia, could be in for heavy rains as Florence plods inland.
Florence, a slow-moving system that forecasters say could release more than 3 feet of rain in places, could end up being even worse.
But forecasters said its extreme size meant it could batter the US East Coast with hurricane-force winds for almost a full day.
Screaming winds bent trees and raindrops flew sideways as Florence's leading edge battered the Carolina coast Thursday. Another 400 people were in shelters in Virginia, where forecasts were less dire.
Meteorologists warned it might be days and weeks after Florence's direct hit before the town sees rising water levels.
The Triangle is under a flash flood warning until 8 p.m. Sunday.
Calls for help multiplied as the wind picked up and the tide rolled in. Its surge could cover all but a sliver of the Carolina coast under as much as 11 feet (3.4 meters) of ocean water, and days of downpours could unload more than 3 feet (0.9 meters) of rain, touching off severe flooding.
Florence made landfall as a Category 1 hurricane at 7:15 a.m.at Wrightsville Beach, a few miles east of Wilmington, not far from the SC line, coming ashore along a mostly boarded-up, emptied-out stretch of coastline. Coastal towns in the Carolinas were largely empty, and schools and businesses closed as far south as Georgia.
The storm's movement, not its strength, has forecasters and officials anxious.
A man attached to a respiratory machine sits in a shelter run by Red Cross before Hurricane Florence comes ashore in Grantsboro, N.C., September 13, 2018. Trump, who spoke with state and local officials on Friday, plans a visit to the region next week.
"We're out of power so we spent the first few hours of the day playing board games with candles".
Others were at home hoping for the best. He said he had trimmed his own trees before the storm.