Watch the storm hit Puerto Rico here:
Late Monday, the storm's downpours forced more than 1,000 Dominicans to evacuate their homes, with some families in low-lying areas fleeing to churches and public buildings. Others hunkered down inside their homes as the winds howled outside and heavy waves pounded the piers and washed onto coastal boulevards.
"We are going to see if the zinc roof resists" the storm, Fidelina Magdaleno, 60, said in her house in Nagua while a chicken dinner was prepared inside without electricity.
Residents earlier had jammed supermarkets and gas stations to get supplies for the storm. Schools were closed and emergency services were placed on alert. At least 33 flights were canceled at Santo Domingo's international airport.
The first hurricane of the Atlantic season was a large system that could cause dangerous mudslides and floods in Dominican Republic, the hurricane center said. It was not expected to make a direct hit on neighboring Haiti, though that country could still see heavy rain from the storm.
Dominican officials said the government had emergency food available for 1.5 million people if needed and the country's military and public safety brigades were on alert.
"We have taken all precautions," presidential spokesman Rafael Nunez said.
Irene is forecast to grow into a Category 3 hurricane late Tuesday as it moves over the warm waters of the Turks and Caicos Islands and the southeastern Bahamas, and could maintain that strength as it nears the U.S. coast.
Florida residents were urged to ensure they had batteries, drinking water, food and other supplies.