Hurricane Florence regained Category 1 strength on September 9 as it continued to track to the U.S. East Coast, according to U.S weather officials.
Virginia, North Carolina and SC have declared states of emergency in preparation for Florence's potential impact.
Florence is expected to intensify over the next 12-36 hours likely becoming a major hurricane by Monday afternoon.
Swells generated by Florence are affecting Bermuda and are beginning to reach portions of the US East Coast.
Florence is moving toward the west near 6 miles per hour (9 km/h), and this general motion was expected to continue on Sunday.
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South Carolina's Emergency Management Division also advised people living on the coast to start making contingency plans.
Cooper's emergency declaration makes it possible to waive the state's transportation rules so North Carolina farmers can harvest and transport their crops to market faster. Tropical storm force winds still blow 80 miles from Helene's center.
The storm brings with it an increasing risk of two life-threatening impacts: storm surge along the coast and freshwater flooding from prolonged rains, the hurricane center said. It is too soon to say where, when or how severe the rainfall might be.
At least 67 named storms have passed within 200 nautical miles of where Florence has been travelling since 1851.
The NHC said the vast storm had maximum sustained winds of almost 75 miles per hour (120 kph), reaching up to 125 miles from its center, as it tracked west-northwestward across the western Atlantic. Florence's immediate threat for residents includes large ocean swells, unsafe rip currents and coastal flooding.
Florence was declared this season's first major hurricane after it quickly developed into Category 3 strength last Wednesday.
A National Hurricane Center graphic showing the potential track for Hurricane Florence, as of 11 a.m. Some forecast models showed Florence slamming into land by late next week, while others indicated the storm would curve away from shore. Admiral Christopher Grady said ships can better weather "storms of this magnitude when they are underway".