Tropical Storm Helene formed over the northwestern Caribbean on Tuesday and triggered a tropical storm warning for the Lower Florida Keys. The storm is forecast to be a major hurricane for the Florida panhandle Thursday.

Forecasters say they expect Tropical Storm Helene in the Caribbean Sea to strengthen rapidly and become a hurricane as it moves north across the Gulf of Mexico on Wednesday toward the U.S.

Florida Gov. Ron DeSantis has declared a state of emergency in dozens of counties ahead of the storm’s arrival as soon as late Thursday.