Haiti and the Dominican Republic are braced for Tropical Storm Isaac, which is approaching Hispaniola.
Isaac, which is expected to hit the island on Friday evening, has strengthened in the past few hours.
It will move on to Cuba and the lower United States by the weekend.
Isaac is also expected to bring rain and wind to Puerto Rico.
The BBC reports several provinces in Cuba are on a state of alert, as well as parts of the Bahamas and the Turks and Caicos islands.
Some 400,000 people in Haiti are still living in makeshift camps since an earthquake in 2010.