Tropical Storm Ophelia (search) strengthened into a hurricane as it stalled 70 miles off the northeast Florida coast Thursday, churning waves that caused beach erosion and drenching Kennedy Space Center (search).

Thursday evening, Ophelia had top sustained winds of 75 mph, just over the threshold to be classified as a hurricane, forecasters at the National Hurricane Center (search) said.

But forecasters said it was still unclear where Ophelia was headed.

If it hits Florida, it would become the third hurricane to strike the state this year and the seventh in the last 13 months.

Downpours from earlier storms had caused flooding in Flagler County, raising anxiety levels about the effect of more rain. Authorities shut down a mile-long stretch of beachfront road in Flagler Beach so transportation workers could shore it up with sand and boulders.

"The storm is eating up our dunes," said Carl Laundrie, communications manager for Flagler County.

Two shelters in Flagler County were being readied as a precaution. In neighboring Volusia County, 12 people had already moved into the county's three shelters.

"In reaction to Katrina, we wanted to be extremely proactive," said Dave Byron, spokesman for Volusia County. Volusia County schools were closed Thursday.

Ophelia is the 15th named storm of the season. At 5 p.m. EDT, it remained nearly stationary. Forecasters predict it should turn out into the Atlantic over the next few days, but that wasn't a certainty.

Storm warnings or watches were posted for Florida's east coast from Sebastian Inlet to Fernandina Beach.

Officials at NASA (search) were also keeping an eye on Ophelia. Last summer, the space agency's launch and landing site took the brunt of three hurricanes, which punched big holes into the massive building where shuttles are attached to their booster rockets and fuel tanks.

Ophelia was the seventh hurricane of the Atlantic season, which began June 1 and ends Nov. 30. Hurricanes Nate and Maria were churning elsewhere in the Atlantic, but neither was considered a threat to the United States.

The season's peak typically occurs from the end of August through mid-September.