A rapidly strengthening Hurricane Irene battered the Dominican Republic and Puerto Rico on Monday and threatened to become the first major hurricane to strike the United States since 2005.
Irene grew into a Category 2 hurricane late Monday, and the National Hurricane Center in Miami said it could become a Category 3 storm today.
"We didn't anticipate it gaining this much strength this early," said center meteorologist Chris Landsea.
Forecasters said it could still be that strong when it passes over the Bahamas and slams into the United States.
Forecast models Monday night had the storm growing to Category 3, with winds of 111-130 mph, and coming ashore on the South Carolina-North Carolina border Saturday evening.
The United States has never gone six years without a major strike. The last time the United States was hit by a hurricane was September 2008, when Ike hit Texas as a Category 2, with 110 mph winds.
That span of good fortune has emergency officials concerned about complacency among U.S. residents, particularly Floridians.
"Sociologists tell us that the human brain tends to forget even major things in five years," said National Hurricane Center spokesman Dennis Feltgen. "So Floridians have likely forgotten the terrible storms of '04 and '05."
Early Monday, hurricane center tracking models showed Irene's path heading for Florida. But by Monday night, the tracks had shifted to the east.
Forecasters warned the track is still uncertain. Depending on its strength, even a hurricane 100 miles out in the ocean could have a major impact on homes along Florida's east coast.
"We're still not out of the woods yet,'' state meteorologist Amy Godsey told Gov. Rick Scott during a briefing in Tallahassee.
Bryan Koon, Florida emergency management director, told Scott he and other emergency managers conferred with the hurricane center, Federal Emergency Management Agency and the Red Cross throughout the day.
With the hurricane season nearing its peak, "this is the kind of thing we're going to see more and more of over the next six or seven weeks,'' Koon told Scott.
On Monday, more than a million people in Puerto Rico were without power as Irene produced up to 10 inches of rain, according to the weather service.
Irene is the eighth named storm of the season, ending a record streak of seven storms that failed to turn into hurricanes this season.
Irene's development into a hurricane marked a significant anniversary for Florida: Hurricane Andrew became a hurricane on the same day in 1992, according to the National Weather Service.
Andrew was one of the most devastating storms in history, causing about $30 billion in property damage. And it was the only hurricane to hit the United States that year.
Times staff writers Marissa Lang and Danny Valentine contributed to this report, which contains information from the Associated Press.