Tropical Storm Isaac has pushed into Cuba after sweeping across Haiti's southern peninsula, where it caused flooding and at least three deaths.
Isaac's center made landfall just before midday near the far-eastern tip of Cuba, downing trees and power lines. The storm's surge caused some flooding in the picturesque city of Baracoa.
Forecasters say the storm is likely to grow into a hurricane as it moves northwest in the Gulf of Mexico off Florida's west coast. It could eventually hit the Florida Panhandle as a Category 2 hurricane with winds of nearly 100 mph.
Gov. Rick Scott has declared a state of emergency in Florida as officials prepare for possible bridge closures, flooding and other problems that could arise.
Vacationers are being urged to leave the Florida Keys. A hurricane warning has been posted for the Keys as well as the west coast of Florida from Bonita Beach south to Ocean Reef and for Florida Bay.
Isaac could bring stormy weather to Tampa, where the Republican National Convention gets under way on Monday.