Florence, the tropical storm churning in the Atlantic Ocean since late last week, is expected to strengthen into a Category 1 hurricane by Monday en route to the southeastern U.S. coast, the National Oceanic and Atmospheric Administration said on Sunday.
The NOAA said that Florence currently has maximum sustained winds to near 75 miles per hour with strong gusts, and is likely to remain "an extremely dangerous major hurricane through Thursday," when it is expected to make landfall in the U.S.
On Saturday, the National Hurricane Center said Florence's precise path remained uncertain, but the NHC said the "risk of direct impact" somewhere between Florida and North Carolina was increasing.
The governors of North Carolina and South Carolina declared states of emergency and urged people to prepare for Florence's arrival. Authorities in Florida said they were closely monitoring the storm.
"Swells generated by Florence are affecting Bermuda and are beginning to reach portions of the U.S. East Coast," the NOAA said on Sunday. "These swells are likely to cause life-threatening surf and rip current conditions."
--Reuters contributed to this article.