CHARLESTON, S.C. — Along much of the East Coast, hotel owners, tourism officials and vacationers are keeping a watchful eye on forecasts today as Tropical Storm Arthur churned off Florida, threatening Fourth of July plans for thousands of people.

A tropical storm warning was issued for parts of North Carolina as the first named storm of the season was expected to strengthen to a hurricane and skim the Outer Banks, a string of narrow barrier islands prone to flooding but popular for beachgoers, as a Category 1 hurricane Friday.

Today’s warning stretched across the entire North Carolina coast, from Little River Inlet near South Carolina north to the Virginia border.

A tropical storm watch for Florida’s east coast was canceled.

The worst of the storm should occur at Cape Hatteras, North Carolina, about dawn Friday, with 3 to 5 inches of rain and sustained winds up to 85 mph, said Tony Saavedra, a meteorologist at the National Weather Service.

The storm should move through quickly and be off the coast of New England later in the day, perhaps making landfall in Canada’s maritime provinces as a tropical storm, he said.