Evacuation orders are in place in the Carolinas and Virginia, and Georgia is in a state of emergency.
The storm's outer bands have reached the Wilmington region, prompting flooding in coastal communities from the hurricane's high storm surges, which forecasters said would be up to 13 feet high.
He added: "This is a very risky storm. Hurricane-force winds extend outward up to 80 miles (130 km) from the centre and tropical-storm-force winds extend outward up to 195 miles (315 km)". Florence is now about 110 east-southeast of Wilmington, North Carolina, and east of Myrtle Beach, South Carolina.
Accuweather reported that its meteorologists "believe that the hurricane will stall and meander near the Carolina coast from Thursday night to Saturday".
On Tuesday, hurricane-force winds stretched 40 miles out from the center, Miller said.
"It doesn't matter where you are", he said.
Speaking to reporters Wednesday, North Carolina Governor Roy Cooper said Florence is a monster of a storm, adding, they are hoping for the best yet preparing for the worst.
At 5 p.m. Thursday, the center of Florence was 100 miles east-southeast of Wilmington, North Carolina, and 155 miles east of Myrtle Beach, South Carolina.
The center of Florence is expected to approach the coasts of the Carolinas today and move over the coast of southern North Carolina and eastern SC tonight and Friday.
With Duke Energy expecting up to 3 million power outages for its 4 million customers, power companies will need an extra hand.
Here is the newest information on Tropical Storm Florence as it lands on the East Coast. "Significant river flooding is expected as a result of excessive rainfall across area hydrologic basins".
Despite all the warnings from numerous authorities, some residents say are planning to ride out the storm.
Officials found a basketball-sized hole in the hotel wall and other life-threatening damage, with some cinder blocks crumbling and parts of the roof collapsing. That means locals and their property could be punished with severe hurricane conditions for days, not hours. On Thursday morning, South 17th Street, usually teeming with commuter traffic by 6:30 a.m., was almost devoid of cars.
Florence could do more than $170bn (£130bn) of damage and affect almost 759,000 homes and businesses, says analytics firm CoreLogic.
Cooper said Thursday evening that he has asked Trump for an enhanced disaster declaration for the state to expedite more federal resources.