Jamaica's government urged people to abandon low-lying areas and find shelter against the strong winds and rain of Hurricane Dean. Troops were placed on alert to help evacuate some residents and prepare for emergency operations.
In recent days, residents and tourists crowded onto flights leaving Jamaica, before the nation closed its airports late Saturday. Many of those who remained on the island stocked up on food and other supplies and boarded up their homes to protect against possible damage.
Dennis Feltgen, forecaster for the National Weather Service in Miami, said some areas of Jamaica should prepare for serious storm conditions, including rainfall of up to 50 centimeters.
"Storm surge of seven to nine feet [more than two meters], and hurricane force winds as high as 145 miles per hour [230 kilometers per hour], with occasional higher gusts," said Dennis Feltgen. "This is a full-blown dangerous, category four hurricane that they [Jamaicans] need to be inside, protecting themselves right now."
Cuba's government also issued a storm watch for communities on its southern coast. Dean is the first hurricane of the Atlantic storm season, which forecasters expect to be more active than normal and produce at least seven hurricanes.
Saturday, Hurricane Dean passed south of the island of Hispaniola, where Haiti and the Dominican Republic suffered minor damage from heavy rains and wind. Dominican officials reported the death of one person who was swept out to sea by a powerful wave. An elderly man drowned in storm waters in Saint Lucia, and two other people died on the island of Dominica in recent days.
Weather forecasters say they expect the storm to continue moving west, and hit the Cayman Islands early Monday and reach Mexico's Yucatan peninsula by early Tuesday.
The governor of the southern U.S. state of Louisiana, on the Gulf of Mexico, has declared a state of emergency in anticipation of the storm. Louisiana is home to New Orleans, which suffered devastating floods in the aftermath of Hurricane Katrina in 2005.
Officials with the U.S. space agency, NASA, said they are shortening the mission of the shuttle Endeavour by one day, because of concerns that the storm could affect conditions at Mission Control in Houston. NASA officials now say the Endeavour is due to land on Tuesday.
