Andrea, the first tropical storm of the 2013 Atlantic hurricane season, has become a post-tropical cyclone, the US National Hurricane Centre said in its latest bulletin.
The storm was located about 90km east-northeast of Raleigh, North Carolina, and was packing maximum sustained winds of around 75km/h, the Miami-based National Hurricane Centre said on Friday.
The centre of Andrea will move north-eastward near the US east coast through Saturday and across Atlantic Canada late Saturday through Sunday.
In South Carolina, authorities said there were no immediate reports of injuries or damage. Scattered power outages were reported in the state, with 2,500 customers losing service.
Tropical storm warnings were in effect for the US Atlantic Coast from South Carolina to Virginia, including the lower Chesapeake Bay, and forecasters warned tropical storm conditions will continue to spread northward in the area.
Andrea could cause tornadoes in coastal areas from North Carolina through Virginia, the hurricane centre said.
The storm buffeted Florida's western coast on Thursday, fuelling several tornadoes, including one that ripped a roof off a restaurant in the city of Gulfport. After swirling over the Gulf of Mexico, the storm made landfall over the Big Bend area, where the Florida peninsula joins the mainland.
The Atlantic hurricane season runs from June 1 to November 30. The US government's top climate agency warned in an annual forecast last month that this year's season could be "extremely active" with 13 to 20 tropical storms, seven of 11 of which are expected to become hurricanes.
Three to six hurricanes could become major at Category 3 or above, with winds of more than 110 mph (177 kph), the National Oceanic and Atmospheric Administration said.