The storm battered the coastline throughout Friday and Saturday with hurricane-force winds and as much as 2ft (60cm) of rain in some areas of North Carolina.
"Hurricanes normally come in and they go inland, which sucks the power out of them as they go over the land", he said.
Four deaths were confirmed by officials as American media reported another, and the storm has wreaked havoc in the Carolinas, lashing the USA states with torrential rain and causing rivers to burst their banks.
"Please be safe and be smart and use your common sense", Cooper added.
Flash flood are expected to his the south-east coast as the storm moves across land.
The Wilmington Police Department said that the mother and her infant were killed on September 14, when the tree fell on their house; the infant's father was rushed to the hospital with injuries.
Wilmington police tweeted that the father was transported to the hospital with unspecified injuries. Paramedics trying to reach her were blocked by debris.
It already had, in Beaufort County and its capital city, Washington, where 300 people were rescued from flooded homes.More news: Bell Canada to Support Apple eSIM in iPhone Xs, iPhone Xs Max
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In Lenoir County, a 78-year-old man was electrocuted attempting to connect extension cords, and another died when he was blown away by high winds while checking on his hunting dogs.
The NHC said Florence had the potential to dump historic amounts of rain on North and SC, as much as 40 inches (one meter) in some places.
Colleen Roberts, public information officer for the city of about 30,000 residents, told Fox News that 200 people had been rescued so far as the Category 1 storm battered the area with strong winds and a life-threatening surge. Carteret County officials said Saturday that two people had died there, but the cause of those deaths couldn't be determined. "And we had no belief it would be as significant an event as it was, â€ he said. â€œThis is a 500- or 1,000-year event. â€Eudy´s family has lived in New Bern since the 1850s, he said".
Some local residents described a harrowing retreat as the storm hit early on Friday.
"I'm anxious about what I might find when I go home, though", she said.
Almost 814,000 homes in North Carolina and 170,000 in SC are without power. North Carolina Emergency Management and FEMA have staged supplies and equipment strategically to respond to the storm, and first responders across the state are ready.
As the storm center shifts farther inland, counterclockwise rotation around the center of circulation will continue to pull in loads of tropical moisture from the Atlantic Ocean and pushing up against the more rugged terrain of central and western North Carolina.
Craven County emergency crews put out the message to people stranded to shelter in place, as 150 people were waiting for help before midnight Thursday.
The White House declared a major disaster in the state and said Donald Trump would visit storm-affected areas next week.