Hurricane Wilma has strengthened into a dangerous Category Five storm, the most powerful a hurricane can be.
It's the 12th hurricane of the season to threaten the Caribbean, and experts think it could cause serious damage in Florida this weekend.
Winds of up to 150mph could hit Cuba, Mexico and the Cayman Islands, which have issued warnings in coastal areas.
Wilma has been blamed for one death already, after heavy rains flooded low-lying communities in Jamaica.
Wilma is expected to head towards southern Florida, where residents are preparing to leave the area.
"People have learned their lesson and know better how to prepare. We're not waiting until the last minute anymore," Andrea Yerger, of Port Charlotte, told reporters.
It's not thought that Wilma will hit New Orleans or parts of Central America which have already been devastated by hurricanes this year.