Hurricane Wilma has already triggered mudslides that killed up to 10 people in Haiti as the storm strengthened rapidly and headed for the Gulf of Mexico on a path towards storm-weary Florida.
The government of flood-prone Honduras warned that Hurricane Wilma posed "an imminent threat to life and property of the people of the Atlantic coast". Neighbouring Nicaragua also declared an alert.
Cuba issued a hurricane watch for the western end of the island from Matanzas to Pinar del Rio, as well as the Isle of Youth. Mexico issued a hurricane watch for its northern Caribbean coast.
Wilma was expected to strengthen into a powerful Category 4 storm on the five-step scale of hurricane intensity, with winds over 209kph by the time it crosses from the Caribbean Sea into the Gulf of Mexico on Friday.
The US National Hurricane Centre's long-range forecast track, which has a wide margin of error, had it crossing southern Florida on Saturday. The state was hit by four hurricanes last year and has been struck by Hurricanes Dennis, Katrina and Rita this year.
Wilma was the 21st tropical cyclone of the Atlantic hurricane season, tying the record for most storms set in 1933. It was also the 12th hurricane and tied the record for most hurricanes in a season, set in 1969. The season still has six weeks to run.
Three hurricanes have already
ravaged Florida this year
Days of steady rain from Wilma caused mudslides that killed at least seven people and as many as 10 in mountainous Haiti, government officials said.
Wilma was not expected to threaten New Orleans or Mississippi, where Hurricane Katrina killed more than 1200 people and caused more than $30 billion of insured damage in August. Katrina was followed in September by Hurricane Rita.
Wilma was also expected to miss the Gulf of Mexico oil and gas facilities that are still reeling from Katrina and Rita.
Wilma was about 295km south of Grand Cayman, the largest of the Cayman Islands, a British colony south of Cuba, the US National Hurricane Centre said on Tuesday night.