Hurricane Erin has been downgraded to a Category 3 hurricane but is gaining in size and raising the risk of life-threatening surf later this week along the U.S.

Hurricane Erin is now a Category 5 storm as it rapidly intensified and threatens the Leeward Islands and Puerto Rico, then will move along the U.S. East Coast

Hurricane Erin forced tourists to cut their vacations short on North Carolina’s Outer Banks even though the monster storm is expected to stay offshore after lashing part of the Caribbean with rain and wind on Monday.

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.

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.

Hurricane Erin dazzled forecasters over the weekend, putting on a spectacular show of strength rarely observed, becoming only the 43rd Atlantic-basin Category 5 hurricane on record and tying Camille in 1969 for the 4th earliest-forming Category 5 ever recorded.

Erin, the first hurricane of the season, exploded to a Category 5 hurricane Saturday, and despite fluctuations in intensity, the storm is remaining formidable this weekend. Here's where it could head in the week ahead.