GREENVILLE, N.C . — Hurricane Florence began its brutish slow-motion collision with the Carolina coasts Thursday, with beach towns cowering under the first bands of lashing rain and storm surge. Onshore wind gusts reached 100 mph.

More than 100,000 people were already without power in North Carolina on Friday night, state officials said, and the number is expected to rise. The major power supplier for North and South Carolina, Duke Energy, warned that up to 3 million customers across the two states could lose power.

At the same time, residents and emergency personnel throughout inland North and South Carolina were working under the grim assumption that the Category 1 storm’s pounding of the coastline would be only the first powerful punch in a fight that could go many rounds and last for many days. It will play out not only among seaside resorts, but also in towns and cities much farther west.

“This may be the first time we’ve experienced such a two-punch from these kind of conditions,” said South Carolina’s governor, Henry McMaster, at a news conference Thursday, speaking about evacuations along the coast as well as the possibility of rain-triggered landslides in the mountains.

Florence is proving to be a lumbering giant, with cloud cover as large as the Carolinas themselves. If, as expected, it dawdles over the region, the storm could drop rainfall of 20, 30 or even 40 inches in some areas. Anxiety is especially high over the fate of all of that water, which will have to go somewhere.

That means a cascading series of complications for a city like Greenville, a handsome college town of 92,000 people set on the banks of the Tar River.

The city lies far inland, but it is connected to the sea by the Tar River, which eventually becomes the Pamlico River as it widens out and flows into the Atlantic.

On Thursday, the city’s spokesman, Brock Letchworth, said Greenville’s first concern is that Florence could drop enough water to create immediate flash flooding.

But he said the city was also worried about a massive salty storm surge roaring westward up the river from the Atlantic. Finally, there is the problem of all the rainfall on the rest of the state, which would have to eventually drain eastward out toward the ocean.

“The winds of Hurricane Florence are upon us,” said Steven Still, director of emergency management for New Hanover County, which includes Wilmington. He said the winds would “stay with us for a considerable period of time.”

Emergency officials said they were particularly concerned about the powerful storm surge, predicted to reach 9 to 10 feet on North Carolina’s barrier islands, possibly producing dangerous flooding of rivers, bays, sounds and estuaries throughout the region.

This article originally appeared in The New York Times.

Richard Fausset, Campbell Robertson and David Zucchino © 2018 The New York Times