One of the strangest, most relentless hurricane seasons on record reached new heights Friday as the plodding approach of Hurricane Jeanne prompted evacuation orders for hundreds of thousands of Floridians and led to high wind warnings that stretched 350 miles from the swamp towns south of Miami to the historic city of St. Augustine.

Forecasters predicted that Jeanne would strike the state's east coast early Sunday, bestowing on Florida the unwanted distinction as the first state since Texas in 1886 to endure four hurricanes in a single year.

"It's weird," said Cary J. Mock, a hurricane historian at the University of South Carolina. "It could be the most costly hurricane season ever."

Only Jeanne's history of erratic behavior gave hope to Florida, which was blasted Aug. 13 by Hurricane Charley, Sept. 5 by Frances and Sept. 16 by Ivan. Jeanne, already responsible for more than 1,000 deaths in Haiti, has meandered across the Caribbean for days, weakening and strengthening, turning south, then north, then west.

Some forecast tracks call for the storm to maintain its quirky nature, perhaps even pulling within miles of Florida, then swerving north and hugging the coastline on the way to North Carolina. But most forecasters seemed to agree Friday that the storm was headed inexorably toward the Florida coast, between Fort Pierce and Cape Canaveral. The storm is carrying 100-mph winds but is expected to strengthen before landfall. A high-pressure zone that covers much of the Eastern Seaboard could push down on Jeanne and alter its course.

If the storm stays on its current track, it will douse areas already battered and saturated by Frances, which caused an estimated $4 billion in damage when it crossed the state after landing on Fort Pierce. The guessing game about Jeanne's final destination was torturous, and public officials worried about "hurricane fatigue."

"I know people are frustrated; they're tired of all this," Gov. Jeb Bush (R) told reporters. "Trust me, their governor is, as well."

More than half a million people had been ordered to evacuate as of late Friday afternoon, far fewer than the 2 million affected by Hurricane Charley evacuations and the 2.5 million asked to leave in advance of Frances. But more evacuations were expected Saturday as forecasters refined their Jeanne predictions.

"People will take it seriously," said Mark Weinberg, a spokesman for St. Lucie County.

Some people in vulnerable areas, such as Miami Beach, have lived for more than a month with shutters on their windows. "It's part of the price we pay for living in a tropical paradise," Miami-Dade County Mayor Alex Penelas said.

Scientists believe that hurricanes are prone to cycles of activity and inactivity. This appears to be a cycle of not just increased, but historic, activity, experts said. Max Mayfield, director of the National Hurricane Center in Miami, said more hurricanes have formed since 1995 than during any other nine-year period in history.

Meteorologists believe the cycles are controlled by water-temperature fluctuations in the frigid north Atlantic, known as "multi-decadal oscillation." Increases in the temperature lead to more hurricanes, Mock said.

The ongoing spate of hurricanes is reminiscent of the early 1900s, Mock said, when mostly undeveloped Florida was pounded by 16 hurricanes of Category 3 strength -- 110-mph winds -- or greater in four decades. Since then, there have been only two: Hurricane Andrew in 1992 and Charley, a Category 4 storm that brought 145-mph winds to Florida's west coast and caused $7 billion in damage in August.

"We could be entering a period just like the early 1900s," Mock said.

Mock will have plenty of time to sort all this out. Jeanne is expected to arrive on Sunday, but the hurricane season does not end until Nov. 30.

Researcher Lucy Shackelford in Washington and special correspondent Catharine Skipp in Miami contributed to this report.

Pam Custis of Fort Pierce, Fla., talks to her son. Forecasters predict Hurricane Jeanne will make landfall near the area Sunday.Gas supervisor Ralph Pujol directs cars in line at the Costco store in Altamonte Springs, Fla., as drivers prepare for the possible strike of Hurricane Jeanne.