At least 188,000 people were without power in North Carolina and SC early on Friday.
Top winds were holding at 90 miles per hour - that's just a Category 1 hurricane - but some communities were already submerged in more than six feet of water as the storm drenched the coast. However, as the storm continues to track south, rainfall totals could increase.
Florence should continue losing strength as it menders along the coast, weakening further as the storm travels across inland SC on Saturday, the weather service said.
Forecasters said catastrophic freshwater flooding is expected well inland over the next few days as Florence crawls across the Carolinas.
"We want people to know they have a place, have a roof over their heads", Langley said.
The hurricane center predicts as much as 101 centimeters of rain for some parts of North Carolina and storm surges as high as 4 meters - taller than many houses. "Hurricane-force winds extend outward up to 80 miles (130 km) from the centre and tropical-storm-force winds extend outward up to 195 miles (315 km)".
In a hurricane, as Live Science has reported, the most significant threat is flooding, not the high winds.
The US National Hurricane Center described how winds of up to 90 miles (150 kilometers) per hour were pummeling the state of North Carolina.
But that, combined with the storm's slowing forward movement and heavy rains, had Gov. Roy Cooper warning of an impending disaster.More news: US, Canada to resume Nafta talks
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And she has seen reports of people fleeing to rooftops to escape high floodwaters.
A state of emergency has been declared in five coastal states - North Carolina, South Carolina, Georgia, Maryland and Virginia. Through Sunday evening, more than 20 inches of rain could fall in southeast North Carolina and far northeast SC on top of what has already fallen.
The centre urges people within the affected areas to take all necessary actions to protect life and property from rising water and the potential for other unsafe conditions.
More than 306,000 residents and businesses, mostly in eastern counties, were without power as of 5 a.m. Friday, according to online updates from Duke Energy, the N.C. Electric Cooperatives and smaller utility companies.
More than 60 people had to be pulled from a collapsing cinderblock motel at the height of the storm.
More than 3,000 inmates at North Carolina prisons and juvenile detention centers were moved out of the storm's path. "Trees are blowing down in the wind".
Forecasters warned that drenching rains of anywhere from 1 to 3½ feet as the storm crawls westward across North and SC could trigger epic flooding well inland over the next few days.