Tropical Storm Idalia is expected to strengthen to a Category 2 hurricane by the time it reaches Florida's Gulf Coast on Tuesday.
Winds could reach up to 100 miles per hour.
The storm could bring heavy rains to Florida, Georgia, and the Carolinas.
A hurricane watch has been issued for a large section of western Florida, extending from Englewood to Indian Pass, and including Tampa Bay.
A tropical storm watch has also been issued for the Gulf Coast south of Englewood to Chokoloskee.
Residents should keep their gas tanks at least halfway full in case emergency evacuation orders are issued.
Gov. Ron DeSantis of Florida has signed an executive order declaring a state of emergency in 33 counties in preparation for the storm.
The combination of the tide and storm surge could bring water levels up to 11 feet in some parts of the Florida coast.