Hurricane Erin strengthened into a Category 2 storm on Friday as it approached the northeast Caribbean, prompting forecasters to warn of possible flooding and landslides.

Erin became a Category 3 hurricane in the Caribbean early Saturday and is expected to strengthen further during the day, the National Hurricane Center reported.

Dangerous surf and rip currents are expected to affect the U.S. East Coast next week, with waves reaching up to 15 feet (5 meters) along parts of the North Carolina coast that could cause beach erosi...