A hurricane warning is in effect for the north coast of the Dominican Republic. A hurricane watch is in effect for the northern coast of Haiti and the central Bahamas.
All of Haiti is under a tropical storm warning.
Haiti, which suffers from extensive deforestation and poor infrastructure, is particularly vulnerable to the heavy rains Irene is expected to bring.
In June, more than 20 Haitians were killed by mudslides and flash floods.
The country is also still struggling to recover from a devastating earthquake in January 2010, which officials said killed as many as 230,000 people, leaving more than 1 million homeless.
According to the International Organization for Migration, some 634,000 Haitians still live in camps; other estimates put that figure at 375,000. CONTINUE