In addition, the threat of storm surges looms for areas in the path of the storm, meaning life-threatening inundation from rising water moving inland is possible.
Asked if he had spoken with President Donald Trump -a politically ally whom McMaster backed very early in the 2016 campaign- the governor says the president reassured him SC would get federal assistance to dig out.
Weinmann pulled 10 people out of flooded neighborhoods and delivered them to a shelter.
Three died in one inland county, Duplin, because of water on roads and flash floods, authorities said.
Utility crews worked to restore electricity.
And on Saturday evening, Duke Energy disclosed that heavy rains had caused a slope to collapse at a coal ash landfill at a closed power station outside Wilmington.
Complicating the move for residents were power outages and road closures.
A reporter for WWAY, the CNN Wilmington affiliate, said the Wilmington firefighters were "shaken up" by what they encountered at the home of the deceased mother and child.
Florence came ashore in the Carolinas Friday and its storm surges, flash floods and winds scattered destruction widely. It said it was located about 60 miles west of Myrtle Beach, South Carolina, and forecasters predicted a slow westward march.
At least five people have died in the state in relation to the storm.
Authorities ordered the immediate evacuation of up to 7,500 people living within a mile of a stretch of the Cape Fear River and the Little River, about 100 miles from the North Carolina coast. Six people died in SC, including four in vehicle accidents and two from carbon monoxide from a portable generator. Forecasters say many rivers across the state still haven't crested - some won't crest until late Sunday or Monday. Storm conditions could also lead to tornadoes and landslides, officials said. A woman in Hampstead, North Carolina died of a heart attack after first responders were unable to reach her fast enough due to downed trees.
Volunteers from all over North Carolina help rescue residents and their pets from their flooded homes during Hurricane Florence September 14, 2018 in New Bern, United States.
In Swansboro, North Carolina, almost 34 inches (85 centimeters) of rain had fallen by Sunday afternoon and 20 other places in North Carolina had at least 20 inches, according to the National Weather Service.
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A total of 40 inches of rain is expected to fall in southern North Carolina, and a total of 20 inches of rain is expected in northern SC and western North Carolina, according to the NWS. Some area residents described a harrowing retreat as the storm hit.
About 1.7 million people in North Carolina, South Carolina and Virginia are under voluntary or mandatory evacuation orders, and millions of others live in areas likely to be affected by the storm.
State Highway Patrol Commander Col. Glenn McNeill said people should stay off the roads.
As of the 5 a.m. update from the hurricane center, the center of the storm is outside of Batesburg- Leesville, a town about 35 miles southwest of Columbia.
Flood waters had receded, and her husband was able to return home to retrieve their vehicle, blankets, food and clothing, Moore said.
"We got them out, but by the time we left, the water was so high that they would have drowned. So yeah, not safe", Ochoa said.
The White House said President Donald Trump would visit hurricane-hit areas next week "once it is determined his travel will not disrupt any rescue or recovery efforts".