Everyone "from SC into the Mid-Atlantic region should ensure they have their hurricane plan in place and follow any advice given by local officials", the hurricane center urged ahead of Florence's expected landfall on Thursday or Friday.
Hurricane Florence, a Category 4 storm, "is expected to be an extremely unsafe major hurricane through Thursday night" and has triggered a hurricane watch for all of North Carolina and part of SC, according to the National Hurricane Center.
If it makes landfall as predicted, Florence could become the northernmost Category 4 hurricane to hit the USA since records were first kept in 1851. The storm was moving northwest at 17mph (28km/h), and was showing signs of strengthening, with category 4 winds of 130mph (215km/h).
As powerful Hurricane Florence crept closer to the southeastern United States on Tuesday, farmers in North Carolina rushed to harvest corn and tobacco and stock up on pig rations, while the danger of deadly flooding threatened a state where millions of farm animals are housed.
If Florence slows to a crawl just off the coast, it could bring torrential rain all the way into the Appalachian mountains and as far away as West Virginia, causing flash floods, mudslides and other unsafe conditions in places that do not usually get much tropical weather.
The worst place to be in a hurricane is the right-front quadrant, where onshore winds are strongest and the storm surge is maximized.
South Carolina's governor ordered the evacuation of the state's entire coastline on Tuesday and predicted that a million people would flee as major roads reverse directions.
"All indications are that the storm will slow down and just crawl or meander over the inland sections and the coastal Piedmont", Weather Channel hurricane expert Bryan Norcross said.
Crews also prepared 16 nuclear reactors in the three-state region for the storm.
Major storms and flooding hit the Carolinas in 2015 and 2016.
Communities in Florence's path could be without electricity for weeks due to downed power lines and flooded equipment, Federal Emergency Management Agency (FEMA) Administrator Brock Long said.
Trump also tweeted about Florence and the Carolinas after being briefed on the storm on Monday. "We want to make sure people understand that people should not ride Hurricane Florence out".
Last year, there were 17 named storms.
For many people, the challenge could be finding a safe refuge.
Days before its arrival, Florence was already disrupting commercial operations.
Duke University in Durham, North Carolina, said classes would be canceled after 5 p.m. on Wednesday, joining other colleges in the state making similar plans.
Tall corn and tobacco crops are most vulnerable to wind damage and hard to harvest if knocked down, said Rhonda Garrison, executive director of the Corn Growers Association of North Carolina. The National Weather Service's Morristown office said Monday that three-to-four inches of rain are possible in upper East Tennessee, around the Tri-Cities, as a result of the hurricane.
"The levels are in pretty good shape to handle the rain, but it all depends on how much rain we get", Ashby said. "Any amounts of money, whatever it takes, we're going to do it".
Landfall is expected late Thursday or early Friday, and on its current path the eye of the storm will pass near Wilmington and the southern beach towns.