The 1st effects were already being seen on barrier islands Monday as unsafe rip currents and seawater flowed over the state highway.
Florence's projected path includes half a dozen nuclear power plants, pits holding coal-ash and other industrial waste, and numerous hog farms that store animal waste in massive open-air lagoons.
In this September 12, 2018 photo provided by NASA, hurricane Florence churns over the Atlantic Ocean heading for the USA east coast as seen from the International Space Station.
My people just informed me that this is one of the worst storms to hit the East Coast in many years. "When you stall a system like this and it moves real slow, some of that rainfall can extend well away from the center".
Hurricane Florence is packing maximum sustained winds of 140 miles per hour and higher gusts on Tuesday morning.
Florence was located about 410 miles south of Bermuda and 975 miles east-southeast of Cape Fear, North Carolina, on Tuesday at 5 a.m.
"The centre of Florence will move over the southwestern Atlantic Ocean between Bermuda and the Bahamas Tuesday and Wednesday, and approach the southeastern coast of the U.S. on Thursday", the NHC said.
Forecasters are also tracking several other hurricanes in the Atlantic and Pacific Oceans.
"Florence is a threat well beyond the coast, so inland counties need to be ready as well", he added.
"Concerns are growing for a large area of the South and North Carolina coasts, waiting on the arrival of Hurricane Florence".
The governors of North and South Carolina, Maryland and Virginia declared states of emergency ahead of the approaching storm.
Up to 30 inches of rain could fall in isolated pockets across North Carolina, Virginia and northern SC through Saturday.
Only three states have laws in place to enforce mandatory evacuations - California, New York and North Carolina, with violators facing misdemeanor charges.
- As the Carolinas undertake a final full day of preparation ahead of Hurricane Florence's landfall, it is still a risky, category 4 hurricane.
And just weeks after Hurricane Lane led to major floods in Hawaii, Hurricane Olivia could hit the state as early as Tuesday.
Liz Browning Fox was planning to ride out the storm on the Outer Banks, defying evacuation orders.
The first of the gusts could arrive in North Carolina at 8 p.m. Wednesday, the center said.
"Florence's upper-level environment is predicted to remain quite favorable while the storm traverses sea surface temperatures of around 29C over the next 48 hours".
What else should I know?
Another airline - ultra-low-cost carrier Allegiant - warned on its website that Florence-related disruptions were possible, but it did not say it was offering fee waivers for flights in the storm's path.
"We're preparing as we're playing the football game on Saturday with all of our travel plans and we'll be in constant communication with South Carolina", Hamrick said. "There is no way to be completely safe", but going inland might not be much safer.
Virginia Gov. Ralph Northam's evacuation order applies to about 245,000 people, including parts of the Hampton Roads area and Eastern Shore.