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.

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.

Tracking Hurricane Erin, the first named storm of the Atlantic hurricane season, which weakened to a Category 3 storm early Sunday.

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.