Florida Governor Rick Scott there could be "catastrophic" damage if Matthew slammed directly into the state. He urged some 1.5 million people there to evacuate.
"If you're reluctant to evacuate, just think of all the people this storm has already killed. You and your family could be among these numbers if you don't take this seriously."
More than 140,000 homes were without power, he added.
Struggle to reach Haitian storm zone
Haitians describe hurricane ordeal