"Preparations to protect life and property should be rushed to completion," the hurricane center warned on its Facebook page.
Matthew could dump up to 25 inches of rain over much of southern Haiti, with "isolated maximum amounts of 40 inches," the hurricane center warned. Eastern Jamaica, the Dominican Republic and eastern Cuba could see 10 to 20 inches of rain with 25 inches in isolated areas.
"This rainfall will produce life-threatening flash floods and mud slides," the weather service warned. In addition, storm surges in the region could cause catastrophic flooding.
Hurricane warnings were in effect for the north coast of Haiti, Jamaica and eastern Cuba. Watches were issued for the Turks and Caicos and southeastern Bahamas and parts of Cuba.
In Haiti, civil protection officials broadcast warnings of a storm surge and big waves, the Associated Press reported. The government urged families to prepare food and water kits. In Jamaica, Prime Minister Andrew Holness told Reuters his nation was braced for the storm, which could be the most severe for his nation since Gilbert killed more than 40 Jamaicans and dumped more than 30 inches of rain in some areas in 1988.
"The impact of the hurricane will probably be similar or greater than Hurricane Gilbert, but our preparedness would be far better," Holness said.
Long lines formed at stores and gas stations as Jamaicans prepared for the worst.
"This is not a joking matter," Desmond McKenzie, minister of local government and community development, told Agence France-Presse. "There is no room for any mischief to be made as we face one of the most severe natural disasters in quite a long while."
Matthew was expected to reach Cuba on Tuesday, potentially making a direct hit on the U.S. Navy base at Guantanamo Bay, base spokeswoman Julie Ann Ripley told AP. She said mandatory evacuation of non-essential personnel was underway, including about 700 family members of military personnel. About 5,500 people living on the base, including 61 men held at the detention center.
A brush with Florida would be several days away.
“It’s too early to rule out what impacts, if any, would occur in the United States and Florida,” Dennis Feltgen, a spokesman for the weather service's Miami Hurricane Center, told AP.