With some homes still swaddled in blue tarp and the deaths from Hurricane Charley (search) still fresh in their minds, Southeastern residents once again warily eyed a menacing hurricane — a storm that could prove the mightiest yet this season.

Nearly a half-million people in Florida were ordered to leave their homes by Thursday afternoon as Hurricane Francis (search) churned toward the U.S. mainland. States of emergency were declared in both Georgia and Florida.

Packing 140 mph winds and a course that has emergency officials in several Southeastern states jittery, the Category 4 storm (search) was expected to fluctuate in intensity as it headed for a Labor Day weekend rendezvous.

Supermarkets along the state's Atlantic coast were stripped of bottled water and canned goods. Home supply stores were filled with people desperate for more plywood, batteries, flashlights and generators.

Reservation clerks of sold-out hotels groaned with each telephone ring, knowing someone seeking a room was on the other end. And demand for gas was so great some stations were pumped dry.

"We can't control the kind of damage that Frances is going to cause, but if people are smart, lives can be saved," said Max Mayfield, the director of the National Hurricane Center in Miami.

Early Thursday, Frances' center was 520 miles east-southeast of West Palm Beach. It was moving west-northwest near 13 mph, and was expected to continue that course for the next 24 hours.

Forecasters said Frances — a Category 4 storm — could begin affecting Florida late Thursday, less than three weeks after Charley raked the state's west coast with 145 mph wind, causing billions of dollars in damage and killing 27 people.

Already, Frances is as strong as Charley, and forecasters said it could become a Category 5 with winds of 156 mph or higher by the time it makes landfall. The difference wasn't something residents spent time discussing.

"Category 4, Category 5, what's the difference? I'm still out of here," said Michele Byrd, 38, a food service executive from Vero Beach. "This one will probably be bigger than Charley. I don't see any way we're not getting hit."

Late Wednesday, the National Hurricane Center issued a hurricane watch for about 280 miles of Florida coast from Florida City to Flagler Beach. A hurricane watch means that those areas could start feeling hurricane conditions within 36 hours.

Court trials were canceled in 10 Florida counties, cruise lines kept their ships away and schools in nine counties were shuttered for Thursday; another three planned to do the same Friday. In St. Lucie County, a curfew was to go in effect Friday night.

The menacing strength of Frances coupled with the damage wrought by Hurricane Charley in Florida had even normally stoic coastal Georgians spooked.

"The people here are paying this one a little more attention than they normally would," said Tybee Island Mayor Walter Parker. "When I went to the Post Office today, some people said they're a little more concerned. They saw what Charley did to Florida."

The storm and evacuations it forces are certain to spoil Labor Day outings and make a mess of holiday travel across the Southeast. Florida may reverse lanes on some highways to handle the evacuation traffic, state Emergency Management Director Craig Fugate said.

Many businesses along the Atlantic coast began closing Wednesday, some not planning to reopen until Sunday at the earliest. Even Cape Canaveral's Kennedy Space Center said it planned to shut down, leery of the havoc Frances could bring.

"It's going to hit somewhere," said Stephanie Graniero, who was having hurricane shutters attached to her store along a deserted commercial strip of Delray Beach. "You have to try to stay calm and not panic. If it's going to hit, you have to be prepared."

An evacuation order was issued for 300,000 Palm Beach County residents, and those who live in mobile homes and flood-prone areas of Volusia, Brevard, Martin and Indian River counties also were ordered to find safer locations. Forecasters said storm surges of 15 feet or more could affect those areas if Frances takes dead aim.

State officials worried about finding enough room in shelters. Many hotel rooms in southern Florida are occupied by emergency workers and people left homeless by Charley. Some schools and community centers are still being used as shelters.

To make matters worse, many rivers and lakes in the Carolinas and Virginia are already swollen with rains from a series of August storms. The most recent of those came Monday, when the remnants of Tropical Storm Gaston brought heavy rain and knocked down trees and power lines.

Joe Farmer, of South Carolina's Emergency Management Division, said the state would likely have to deal with Frances even if it makes landfall in Florida since evacuees would head north on Interstate 95.

The last time two major storms hit Florida so close together was 1950, when Hurricane Easy hit the Tampa area and Hurricane King struck Miami about six weeks later. Neither of those storms were as powerful as Charley or Frances.