The first named tropical system has formed in the Gulf of Mexico just off the Florida coast.
The National Hurricane Center says an air force reconnaissance plane was able to identify a well-defined circulation.
A tropical storm warning is in effect from Boca Grande to the Ochlockonee River on Florida's west coast. A tropical storm watch is in effect from Flagler Beach to Surf City, North Carolina.
A flood watch is in effect for the entire area until Friday afternoon.