Hurricane Wilma is threatening Cuba and Mexico and is expected to strengthen as it ploughs north through the Caribbean.
Heavy rainfall flooded several low-lying communities in Jamaica
It has grown into a Category 2 storm, packing winds of 110mph (160km/h) and unleashing heavy rain over the region.
Wilma is the 12th hurricane of the season, a number reached only once before - in 1969 - since records began.
The hurricane could hit western Cuba or the Yucatan Peninsula before heading into the Gulf of Mexico and Florida by the weekend.
A hurricane watch remained in effect for the Cayman Islands, while Honduras was on alert for a tropical storm.
In Jamaica, heavy rainfall flooded several low-lying communities, blocked roads and forced 100 people into shelters, according to local officials.
Rain is also falling on Haiti and Cuba, which is preparing to evacuate four southern provinces threatened with floods.
A number of countries in storm-battered Central America have issued alerts.
The authorities in Honduras are preparing for evacuations.
"We are not going to wait for the storm to hit," said emergency commission chief Luis Gomez.
Meanwhile, neighbouring Nicaragua and El Salvador are keeping a close eye on the storm's course.
The US Hurricane Center in Miami said that Wilma's path may take it away from the US Gulf Coast.
But it could strengthen to a Category 4 as it crosses from the Caribbean into the Gulf.
Vulnerable areas like the Florida Keys island chain are preparing to evacuate residents.
And despite the apparently receding threat further west, New Orleans' mayor Ray Nagin warned residents to prepare for another evacuation if the storm moved toward the city which was only pumped dry from the floods of Katrina and Rita last week.
"We are going to continue to monitor the storm and at a moment's notice people should be ready to evacuate", he said.
Wilma has raised concerns regarding oil production in the Gulf of Mexico.
The areas threatened by the new hurricane are still recovering from the devastation caused by hurricanes Katrina and Rita.
Nearly 1,200 people were killed in the US by Katrina in August, and hundreds more died in Mexico and Central America when Hurricane Stan struck early this month.
HURRICANE WILMA, 18 OCTOBER 2005
Source: United States National Hurricane Center