A National Weather Service forecaster has said it will be the "storm of a lifetime" for parts of the Carolina coast. The storm is expected to slowly move inland, battering much of the U.S. coast for days. "Now it's just taking the brunt of the storm".
"It can not be emphasized enough that the most serious hazard associated with slow-moving Florence is extremely heavy rainfall, which will cause disastrous flooding that will be spreading inland through the weekend", the National Hurricane Center said in its 5 a.m. update.
Latest reports have the center of Florence approaching the coasts of North and SC on Thursday.
There will be hurricane-force winds up to 80 miles from the centre of the storm, meteorologists say.
About 10 million people are in the sights of the storm as it zeroes in on the Southeastern coast.
"There is still time, but not a lot of time", said Derrec Becker of the South Carolina Department of Emergency Management.
More than 400,000 people were without power in North Carolina as of early Friday morning, as Hurricane Florence pounded the region with strong winds and heavy rains.
About 5.25 million people live in areas under hurricane warnings or watches, and 4.9 million live in places covered by tropical storm warnings or watches, the National Weather Service said.
These same areas that are inundated with storm surge will also be hammered by damaging winds sustained at 50 to 70 miles per hour with gusts as high as 80 to 90 miles per hour - strong enough to damage homes and buildings, down trees and knock out power.
Hurricane Florence was downgraded to a Category 1 storm with a 10-foot storm surge but forecasters have warned the downgrade will not affect the potential threat of the storm.
President Donald Trump both touted the government's readiness and urged people to get out of the way.
"That's the second story of a house", he said. The core was also about 60 miles (95 kilometers) east-southeast of Wilmington, North Carolina.
Florence's expected slowdown means a prolonged period near the coast, said the hurricane center's Joel Cline.
The storm could dump 20 to 30 inches of rain along the Carolina coast and up to 12 inches inland.
Schools and businesses closed as far south as Georgia, airlines canceled more than 1,500 flights, and coastal towns in the Carolinas were largely emptied out. Home Depot and Lowe's activated emergency response centers and sent in around 1,100 trucks to get generators, trash bags and bottled water to stores before and after the storm.
Duke Energy told Fox News 3 million customers, which represents about 75 percent of their customers in the Carolinas, could lose power. Workers are being brought in from the Midwest and Florida to help in the storm's aftermath, it said.
Computer models of exactly what the storm might do varied, adding to the uncertainty.
"I ask all Georgians to join me in praying for the safety of our people and all those in the path of Hurricane Florence", Deal said.
Their entire neighborhood evacuated in Wilmington, David and Janelle Garrigus planned to ride out Florence at their daughter's one-bedroom apartment in Charlotte. They are stuck in their attic and their home is flooded.
He said if something catastrophic happens to his home, he plans to make his way to a neighbor's house.
Others were at home hoping for the best.
But forecasters warned that the widening storm - and its likelihood of lingering around the coast day after day - will bring seawater surging onto land and torrential downpours.
Meanwhile, winds and rain were expected to arrive later in SC, and a few people were still walking on the sand at Myrtle Beach while North Carolina was getting pounded.
But many other animals will be kept in barns. "Today the threat becomes a reality", he said. "You feel like you should have already left". "Also, a little creepy".
The Associated Press contributed to this article.