Hurricane Erin has strengthened into a Category 2 storm as it approaches Puerto Rico and the Virgin Islands, bringing heavy rains that could cause flooding and landslides.

Beaches are being closed at some locations along the US East Coast as Hurricane Erin threatens rip currents from Florida to New England.

The first Atlantic hurricane of the season is forecast to bring heavy rain and life-threatening surf and rip currents to the U.S. East Coast this week.

Storms that ramp up so quickly complicate forecasting and make it harder for government agencies to plan for emergencies. Hurricane Erick, a Pacific storm that made landfall June 19 in Oaxaca, Mexico, also strengthened rapidly, doubling in intensity in less than a day.

A disturbance in the Atlantic following Hurricane Erin is now expected to track northward, National Hurricane Center data shows.

While the category 4 storm is not expected to make landfall on the U.S. east coast, it will have an impact nonetheless. Dangerous high surf and rip currents are expected from Florida to New England throughout the week.

The storm, still driving dangerous, 125 mph winds, was centered about 310 miles northwest of San Juan, Puerto Rico, at around 8 p.m. ET on Sunday, the hurricane center said. Just a day earlier, Erin's sustained winds had reached 160 mph. A mandatory ...