Late Wednesday, the Navy ordered the Second Fleet to prepare to move ships out of the way of the storm beginning early Thursday.
In the Bahamas, tourists cut their vacations short and caught the last flights out before the airport was closed. Those who remained behind with locals prepared for a rough night of violent winds and a dangerous storm surge that threatened to punish the low-lying chain of islands. Irene has already hit Puerto Rico and the Dominican Republic, causing landslides and flooding homes. One woman was killed.
On the Outer Banks of North Carolina on Wednesday, some tourists heeded evacuation orders for a tiny barrier island as Irene strengthened to a Category 3 storm, with winds of 120 m.p.h.
"We jam-packed as much fun as we could into the remainder of Tuesday," said Jessica Stanton Tice of Charleston, W. Va.
Officials said Irene could cause flooding, power outages, or worse as far north as Maine, even if the eye of the storm stays offshore. Hurricane-force winds were expected 50 miles from the center of the storm.
Predicting the path of such a huge storm can be tricky, but the National Hurricane Center uses computer models to come up with a "cone of uncertainty," a three-day forecast that has become remarkably accurate in recent years. Forecasters are still about a day away from the cone reaching the East Coast. A system currently over the Great Lakes will play a large role in determining if Irene is pushed farther to the east in the next three or four days.
Officials along the Jersey Shore were also watching the course of the storm and preparing for heavy rain and damaging winds. "You just don't know what's going to happen," said Barbara Steele, director of Ocean County's Department of Public Affairs and Tourism.
Diane F. Wieland, Cape May County's director of tourism, said officials were encouraging residents and tourists "to find a safe route out before hits the area. "There can be a bottleneck if everybody is going out at the same time," she said. Wieland noted that people should also be aware of "higher tides because of the new moon. . . . There will be wave action and rain."
In New England, beachgoers second-guessed vacation plans. Steven Miller, who runs a charter fishing company off Rhode Island, hasn't received any cancellations, but no one has been calling to schedule trips in the next few days, either. "The hoopla beforehand could end the season," he said. Sandbags were in demand in the Northeast to protect already-saturated grounds.
The uncertainty of the storm's path had some moving up events.
Officials still hadn't decided whether to postpone Sunday's dedication of the Rev. Dr. Martin Luther King Jr. memorial on the National Mall. Hundreds of thousands were expected for that event.
Staff writer Edward Colimore contributed to this article.