The hurricane watch in North Carolina covers an area from Bogue Inlet to Oregon Inlet, including Pamlico Sound. A tropical storm watch is in effect for parts of Florida and South Carolina.
The storm's maximum sustained winds early Wednesday are near 60 mph (95 kph). The U.S. National Hurricane Center says Arthur is expected to strengthen and become a hurricane by Thursday.
Arthur is centered about 90 miles (145 kilometers) east of Cape Canaveral, Florida, and is moving north near 6 mph (9 kph).
The Hurricane Center urged those as far north as parts of Virginia to monitor Tropical Storm Arthur's path.