Hurricane Wilma is the strongest ever recorded, US weather experts have said.
Wilma blew up into a category five storm on Wednesday, which is the most powerful a hurricane can be.
The storm's 'barometric pressure', which is a measure of its strength, is the lowest ever on record in the area known as the Atlantic basin.
Wilma is heading towards Cuba, Mexico and the Cayman Islands, and is seen as a threat to Florida. Many people have left their homes already.
Hurricane Wilma now has winds of up to 175mph and very heavy rains.
It's the 12th hurricane of the season to threaten the Caribbean.
Wilma has been blamed for one death already, after rains flooded low-lying communities in Jamaica.
But people in Florida said they were prepared for the storm hitting at the weekend.
"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.