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

Hurricane Erin will continue to strengthen as it approaches the Leeward Island and Puerto Rico, where it will threaten with tropical downpours, pounding surf and strong winds.

Erin, the first hurricane of the season, is now forecast to become a Category 4 by Sunday. Here's where it could head in the week ahead.