"This will likely be the storm of a lifetime for portions of the Carolina coast", the National Weather Service in Wilmington, N.C., said, "and that's saying a lot given the impacts we've seen from hurricanes Diana, Hugo, Fran, Bonnie, Floyd, and Matthew".
So, what's the worst that could happen?
German astronaut Alexander Gerst posted photos of the massive hurricane online from space.
The images, captured from249 miles above the storm, captured Florence as it draws close to North Carolina's coast.
Hurricane Florence has been downgraded to a Category 2 storm but it is still considered an extremely unsafe and life-threatening storm.
Florence's top sustained wind speeds dropped from a high of 140mph to 110mph which reduced the hurricane's power from Category 4 to Category 2.
Florence is forecast to dump up to one metre of rain in some areas after it makes landfall in North and SC.
Elsewhere in the Atlantic basin, Tropical Storm Isaac will strike the islands of the Lesser Antilles, with Guadeloupe, Dominica and Martinique under a tropical storm warning.
Analytics firm CoreLogic predicts that the damage from Florence could be more than $170 billion - making it the most expensive hurricane to hit the continental U.S. The downtown area was underwater.Calls for help multiplied as the wind picked up and tide rolled in, city public information officer Colleen Roberts said.
Kevin Miller, a 50-year-old electrician, said he planned to ride out the storm at his home near Charleston. "Please heed the warnings", Mr Brock said: "Your time is running out". "I would go visit a relative somewhere away from the shoreline".
"People do not live and survive to tell the tale about what their experience is like with storm surge", he said.
A view of Hurricane Florence is shown churning in the Atlantic Ocean in a west, north-westerly direction heading for the eastern coastline of the U.S., taken by cameras outside the International Space Station.
That's because in addition to the extensive flooding, the hurricane is expected to knock out power along the coast, according to an analysis done by a team headed by Seth Guikema, an associate professor of civil and environmental engineering at the University of MI. The agency is in constant contact with the South Carolina Emergency Management Division. Rather than pushing up toward western Virginia, the storm's center is now predicted to move across eastern SC on Friday night and Saturday.
Almost 1000 prisoners in SC will not be moved from their cells, despite a mandatory evacuation order in the area. Now hurricane "Florence" waiting in Washington, where he also declared a state of emergency. In North Carolina, Cooper says, "2,800 soldiers will be on active duty, joined by even more on standby".
However, since the Fukushima disaster in 2011, US power plants have installed more safety equipment, such as waterproofing, portable pumps and generators, Duke Energy spokeswoman Mary Kathryn Green told Reuters.