The storm threatened to hit coastal North and SC with 215km/h winds and massive waves when it makes landfall on Friday, and its rains will take a heavy toll for miles inland, the National Hurricane Center in Miami warned.
As of Sunday night, the hurricane was centered in southeast Bermuda and moving west at 7 miles per hour.
The Atlantic hurricane's maximum sustained winds have increased to almost 130 miles per hour (195 kilometers per hour), the National Hurricane Center (NHC) said in an advisory issued at noon Eastern Time (1600 GMT).
The hurricane roared from a Category 1 (90 mph) to a Category 4 (130 mph) in just 13 hours, an extremely rapid intensification, Colorado State University meteorologist Phil Klotzbach said. "Theses swells will result in life-threatening surf and rip currents".
"Florence is. expected to remain an extremely unsafe major hurricane through Thursday", the hurricane center warned.
"To the incredible citizens of North Carolina, South Carolina and the entire East Coast - the storm looks very bad!" wrote the president, who cancelled a planned rally Friday in Jackson, Mississippi in light of the approaching storm.
"It's nearly certain there will be some impact on Charlotte, but it depends on the track", meteorologist Jake Wimberley said from the weather service's office in Greer, S.C. The office forecasts for the western Carolinas including Charlotte.
If Florence tracks northward toward Greensboro, he said, Charlotte could still see significant winds.
Though the NHC can't pinpoint with certainty the exact location and magnitude of the impacts, they said, "interests at the coast and inland from SC into the mid-Atlantic region should closely monitor the progress of Florence, ensure they have their hurricane plan in place, and follow any advice given by local officials".
Now is the time for employers in the path of the storm to start preparations and work with employees to make sure everyone stays safe. North Carolina Governor Roy Cooper told a news conference his state was in "the bull's eye".
A Category 4 hurricane with 105 miles per hour winds is bearing down on the US East Coast, bringing a risk of devastating floods - and there are two more hurricanes behind it.
Hurricane Florence has the potential to bring catastrophic flooding to areas of the eastern United States already soaked by heavy rain and may be the strongest storm to hit the region in decades.
As of Monday evening, Florence was 500 miles in diameter, much larger than the typical 300-mile-wide hurricane.
Handout via Getty Images Hurricane Florence is seen traveling west over the Atlantic Ocean on September 10, 2018.
Arnold also captured hurricanes Isaac and Helene lining up behind Florence in the Atlantic.
"It is still potent, unsafe storm".
"That scenario has a high probability of occurring in North Carolina and Virginia and possibly portions of neighboring states in the Southeast, Appalachians and mid-Atlantic late this week and this coming weekend", Sosnowski added.
As of 11 a.m. EDT on Monday, Florence has been upgraded to a Category 4 storm. The NHC expects Isaac to weaken as it approaches the Caribbean.