Hurricane, tropical-storm and storm-surge watches and warnings now cover 10 million people from North and SC to Virginia.
A buoy off the North Carolina coast recorded waves almost 30 feet (9 meters) high as Florence churned toward shore.
Myrtle Beach's Ocean Boulevard was practically empty at midday on Wednesday, September 12, as the SC town prepared for the arrival of Hurricane Florence.
The centre of Florence, a slow-moving Category 3 hurricane on the five-step Saffir-Simpson scale, is expected to strike North Carolina late Thursday or early Friday and could drift southwest along the coast before turning inland, according to the National Hurricane Center in Miami.
Although Florence was downgraded from Category 4 status, it is still considered an extremely risky storm with maximum sustained winds near 125 miles per hour.
It is predicted the Carolinas could begin feeling tropical storm force winds early Thursday.More news: HRW accuses China of conducting 'human rights violations' against Muslims
Hurricane Florence evacuees were met with standstill traffic on Interstate 95 late Wednesday afternoon extending more than 30 miles north of the South Carolina-Georgia border, according to the South Carolina Department of Transportation's 511 traffic map.
Florence is a large hurricane and will affect much of North and SC.
Forecasters said that given the storm's size and sluggish track, it could cause epic damage akin to what the Houston area saw during Hurricane Harvey just over a year ago, with floodwaters swamping homes and businesses and washing over industrial waste sites and hog-manure ponds.
The Union Point Park Complex is seen flooded as the Hurricane Florence comes ashore in New Bern, North Carolina, U.S., September 13, 2018.
'North Carolina, my message is clear: Disaster is at the doorstep, and it's coming in'.
Maryland, North Carolina, South Carolina, Virginia and Washington states have all already declared states of emergency ahead of the storm.More news: Nintendo Switch Getting Classic NES Controllers
The first tropical storm-force winds were forecast to hit the coast on Thursday.
With their entire neighborhood evacuated in Wilmington, North Carolina, David and Janelle Garrigus planned to ride out Florence at their daughter's one-bedroom apartment in Charlotte.
Some of these reactors - including Duke Energy's Brunswick and Harris nuclear plants in North Carolina and Dominion Energy's Surry plant in Virginia - may be directly in the hurricane's path, Reuters reported.
The "Hurricane Hunter" is specially equipped and operated by the US National Oceanic and Atmospheric Administration to fly through storms to collect data, playing a major role in hurricane forecasting. "It's going to happen".
Another four million people are under a tropical storm watch. "We've just never seen anything like this". Shelters in the city were filling and some people were being bused inland to Raleigh, even though some residents there were told they might have to evacuate because of flooding. Some reactors are undergoing prestorm checks now, and their reactors will be shut down 12 hours before the hurricane arrives, Green said. "But no matter how bad it's going to be, it will pass and our job will be to rebuild this community together".More news: US fighter jets intercept two Russian bombers near Alaska