Mexico, Cuba and Florida have ordered tens of thousands of people to leave areas threatened by a major hurricane.
Honduras has also issued an alert
Hurricane Wilma, a powerful Category Four storm, has winds of 150mph (240km/h) and its rains are lashing outlying areas.
At least 11 people have been killed in Haiti by floods and landslides.
Forecasters say Wilma will brush Mexico's Yucatan peninsula in the next 24 hours, but it is not clear where the hurricane will head next.
At one stage, Wilma was the strongest hurricane ever recorded, and the US National Hurricane Center has warned it remains "potentially catastrophic".
As of 0900 GMT on Thursday, the centre of the hurricane was about 195 miles (315km) south-east of Cozumel, Mexico.
Wilma is moving at a speed of 8mph (11km/h) towards the Yucatan peninsula, but is expected to turn north-west on Thursday, the US National Hurricane Center said.
It said the storm was expected to dump up to 63cm (25 inches) of rain in mountainous areas of Cuba until Friday, and up to up to 38cm (15 inches) in the Caymans and Jamaica until Thursday.
Forecasters say the hurricane presents a "significant threat" to Florida, which it is expected to hit this weekend.
At one stage, the storm measured the lowest barometric pressure on record in the Atlantic basin - a measure of its strength.
The Mexican authorities have told tourists to leave high-risk areas along the coast near the holiday resort of Cancun.
The strong winds have forced music television station, MTV, to postpone its Video Music Awards Latin America, which had been scheduled to take place in the resort of Playa del Carmen.
The Central American states of Honduras and Nicaragua have also issued alerts, and are expecting tropical storm conditions within the next 36 hours.
Cuba began moving coastal residents and suspended school in the western province of Pinar del Rio.
Officials in the vulnerable Florida Keys island chain have ordered visitors and non-residents to leave immediately.
About 80,000 residents are expected to be asked to leave.
Wilma could "cause tremendous damage and loss of life if we're not careful," said Hurricane Center director Max Mayfield.
"The storm surge and the wave action will be tremendous with this hurricane, given the intensity and the size."
Wilma is the record-tying 12th hurricane of the season, the same number reached in 1969.
It is the most for one season since record-keeping began in 1851.
The areas threatened by the new hurricane are still recovering from the devastation caused by hurricanes Katrina and Rita.
Hurricane Katrina killed nearly 1,200 people along the US Gulf Coast in August. Hundreds more died in Mexico and Central America when Hurricane Stan struck early this month.
Mexico: Tourists told to leave high-risk coastal resorts
Cuba: Coastal residents evacuated and some schools closed
US: Visitors and non-residents ordered to leave Florida Keys