Forecasters at the U.S. National Hurricane Center in Miami said Monday night that a hurricane hunter aircraft measured maximum sustained winds of 100 mph (155 kph).
The storm raked Puerto Rico with strong winds and rain. It is spinning just north of the Dominican Republic on a track that could carry it to the U.S. Southeast as a major storm by the end of the week.
The first hurricane of the Atlantic season was a large system. Irene is forecast to grow into a Category 3 hurricane with winds of 115 mph (184 kph) over the Bahamas on Thursday.
It could be that strong as it heads to the U.S. coast. It could perhaps land in Florida, Georgia or South Carolina.