The University of North Carolina canceled its scheduled home game against the 18th-ranked University of Central Florida in Chapel Hill due to the storm's expected landfall.
The slow-moving storm, the most severe hurricane to threaten the US mainland this year, was located about 785 miles (1,260 km) southeast of Cape Fear, North Carolina, at 4:30 p.m. EDT (2030 GMT), according to the NHC. "It's going to destroy homes", said Jeff Byard, an official at the Federal Emergency Management Agency.
A state of emergency has been declared in both North and SC.
Trump, who has faced criticism for his administration's response to Hurricane Maria in 2017, which killed an estimated 3,000 people in the US territory of Puerto Rico, knocked out power to all 3.4 million residents of the Caribbean island, with thousands still without power even six months after the storm hit, said the federal government was "totally prepared" for Florence.
"This will be a storm that's going to be far larger than we have seen in perhaps decades", Trump said.
"While some weakening is expected on Thursday, Florence is expected to be an extremely risky major hurricane through landfall", forecasters said.
Critics slammed the response to Maria compared to FEMA's response to Hurricane Harvey, which hit the mainland USA around the same time.
He said Florence could rival the impact of Hurricane Hugo, which wreaked $7bn (£5.3bn) in damage and claimed 49 lives in 1989.
NHC director Ken Graham admitted: "This one really scares me". Charles Mullen, 81, a longtime resident of Hatteras Island, North Carolina, said he had ridden out many storms and that most locals were planning to stay unless Florence took aim at Hatteras.
Hurricane Florence - the most powerful storm to threaten the Carolinas in almost three decades - is expected to strengthen, say forecasters.
"As we have seen with hurricanes in most recent years, such as Lane in Hawaii earlier this summer and Harvey last year in Texas, feet of rain can fall when these tropical storms stall", AccuWeather's Alex Sosnowski said. Since then, thousands of people have moved to the coast.
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 huge lagoons.
"I must confess I like the atmosphere around it", he said, looking out over the Atlantic.
Duke Energy spokesman Ryan Mosier said operators would begin shutting down nuclear plants at least two hours before hurricane-force winds arrive.
People living on the coastal barrier islands have been issued with a mandatory evacuation order by Governor Cooper for the first time in history. "With the storm of this magnitude, the planning factors, and everything, we will meet the needs".