While it was too soon to project Hurricane Florence’s precise trajectory and timing, forecasters said areas from South Carolina up through Virginia should prepare for the storm, which could approach the coast on Thursday.
With winds currently approaching nearly 85 miles an hour, Florence is expected to turn into a dangerous Category 4 hurricane. Coastal areas could face storm surges and flooding, while communities farther inland will be at risk of prolonged rainfall.
“Florence is forecast to rapidly strengthen to a major hurricane by Monday and is expected to remain an extremely dangerous major hurricane through Thursday,” the National Hurricane Center said.
As of Sunday, Hurricane Florence was southeast of Bermuda. It has fluctuated between hurricane and tropical-storm status while heading west across the Atlantic.
North Carolina Gov. Roy Cooper declared a state of emergency on Friday, and South Carolina Gov. Henry McMaster followed suit the next day, warning residents to begin making preparations.
In South Carolina, Georgetown County and Horry County, which includes Myrtle Beach, increased their readiness level for Florence on Sunday. Local emergency officials laid out potential evacuation zones for residents and urged people to gather supplies ahead of the storm.
At a news conference Sunday, Mr. McMaster said that while much was still uncertain about the storm, Florence was “likely going to be a strong hit on South Carolina.”
“We know we’re going to have a lot of wind and a lot of rain,” he said.
At least so far, this hurricane season has been comparatively mild compared with 2017 when the U.S. was hammered by three successive storms—Harvey, Irma and Maria.
But two other storms are brewing behind Florence. According to the National Hurricane Center, Helene had turned from a tropical storm into a hurricane by Sunday afternoon, and tropical storm Isaac was expected to reach hurricane strength by Sunday evening or Monday.
For now, though, Florence is the most pressing threat.
Ray Ciorra, an assistant manager at a Home Depot store in Myrtle Beach, said the store has had to place emergency orders to restock supplies because of a steady crowd of customers in advance of the storm.
“We’ve had people asking for generators, water, plywood, flashlights,” he said.
Mr. Ciorra said that locals were used to the coastal Carolinas being battered by storms and had grown accustomed to the ritual of gathering emergency supplies before a big hurricane.
“Nobody is panicking,” he said.