The rainfall may produce life-threatening flash floods. "With the size and the intensity and the current forecast track, it's a unsafe time for people in North Carolina with regard to this storm".
Cooper and his counterparts in neighbouring SC and Virginia ordered about 1 million people to evacuate coastal homes, including along the Outer Banks barrier islands.
The chief meteorologist for WCBD-TV in South Carolina, Rob Fowler, told the BBC that Florence was getting bigger, and those even 100 miles away would feel the impact.
More than 400 hundred officers from the South Carolina Law Enforcement Division will be stationed in the coastal areas to help assists evacuation and protect property. A hospital in Hampton, Virginia, was transferring patients to safer places.
A hurricane watch was in effect for Edisto Beach, South Carolina, to Virginia's southern border, and the first hurricane-force winds arriving late Thursday.
"We are sparing no expense".
Delta Air Lines said it will cap airfares in airports from Virginia to Georgia, which could be affected by the storm.
The storm forced people to cut their vacations short along the coast.
But, it's the water, not the wind, that has the potential to make the storm so deadly, experts say.
The Federal Emergency Management Agency (FEMA) is warning residents on the eastern seaboard ahead of Hurricane Florence, calling it a "dangerous" and life-threatening storm.
Not everyone was in a hurry to leave.
Mr Graham said: "The water could overtake some of these barrier islands and keep on going".
"If it decides to come here, we're gone", he said.
People across the region rushed to buy bottled water and other supplies, board up their homes or get out of town.
As skies fluctuated Tuesday between heavy showers and occasional bright spots, a certain sunny outlook swaddled Wrightsville Beach, despite the looming arrival of Florence's heavy winds and inundating rains that has prompted widespread evacuations along the southeastern United States coast.
Wall Street was sniffing out companies that could gain or lose at the storm's hands.
Meanwhile, there are two other storms in the vicinity - Isaac and Olivia have become tropical storms, with Isaac heading for the Caribbean and Olivia set to hit Hawaii early on Wednesday.
If heavy rains also hit SC, the resulting flooding could be devastating.
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