Forecasters say the storm could re-intensify into a major hurricane.
While Erin is unlikely to make landfall along the East Coast before turning farther out to sea, its outer edge packing tropical force winds was approaching North Carolina's Outer Banks.
Water began pouring onto the main route connecting the barrier islands and around a handful of stilted homes precariously perched above the beach.
Authorities expect the largest swells during high tide will cut off villages and vacation homes on the Outer Banks and whip up life-threatening rip currents from Florida to New England.
New York City closed its beaches to swimming on Wednesday and Thursday. Some beaches in New Jersey, Maryland and Delaware are also temporarily off-limits.
Off Massachusetts, Nantucket Island could see waves of more than 3 metres later this week.
Surfers flocked to the oceanfront in Virginia Beach, where Erin was supplying robust waves for the East Coast Surfing Championships and the kind of swells that many locals hadn't seen in awhile.
The championships will pause Thursday when Erin blows directly off the Virginia coast.
Despite beach closures elsewhere, some swimmers were continuing to ignore the warnings. Rescuers saved more than a dozen people caught in rip currents at Wrightsville Beach in North Carolina on Tuesday— a day after more than 80 people were rescued.
A combination of fierce winds and huge waves — estimated to be about 6.1 metres - could cause coastal flooding in many beachfront communities, North Carolina officials have warned.
Dozens of beach homes already worn down from chronic beach erosion and protective dunes could be at risk, said David Hallac, superintendent of the Cape Hatteras National Seashore.
The National Hurricane Centre is also watching two tropical disturbances to the east of Erin that could develop into named cyclones. With thousands of miles of warm ocean water, hurricanes known as Cape Verde storms are some of the most dangerous that threaten North America.
Erin has become an unusually large and deceptively worrisome storm, with its tropical storm winds spreading across 800 kilometres.
It remained a strong Category 2 hurricane on Wednesday with maximum sustained winds around 180 kph, the National Hurricane Centre said.
Erin was about 480 kilometres south-southeast of North Carolina's Cape Hatteras.
Climate scientists say Atlantic hurricanes are now much more likely to rapidly intensify into powerful and catastrophic storms fuelled by warmer oceans.
18°C