KEY WEST, Fla.—Residents and tourists in the Florida Keys prepared Saturday for Tropical Storm Fay, which forecasters said could strengthen to a hurricane and begin battering the island chain as soon as Monday.

Florida Gov. Charlie Crist declared a state of emergency because Fay “threatens the state of Florida with a major disaster,” he wrote in an executive order.

Forecasters predicted Saturday afternoon that the sixth named storm of the 2008 season would make landfall somewhere along western coast of Florida on Tuesday as a hurricane, said Corey Walton, a hurricane support meteorologist at the National Hurricane Center in Miami.

Officials in the Keys’ Monroe County said they would likely order an evacuation of all visitors on Sunday morning. A decision on whether to require all residents to evacuate was to come, county spokeswoman Becky Herrin said.

Keys emergency officials often take the precaution of ordering early evacuations when a storm threatens, because traffic can back up for miles on the single highway to Florida’s mainland.

Besides the threat of high winds, most of the islands sit at sea level andcould be flooded by a storm surge. Flooding from the storm on Saturday killed four people in the Dominican Republic and Haiti.

At 8 p.m. EDT, the storm’s center was about 60 miles southwest of Guantanamo, Cuba, and moving west at 14 mph. It had maximum sustained winds of 45 mph. To become a hurricane, sustained winds must be at least 74 mph.

State officials in Tallahassee opened their emergency operations center, said Blair Heusdens, a spokeswoman for the state’s Division of Emergency Management.

Tourists and locals still packed downtown Key West on Saturday, seemingly unfazed by the approaching storm.

Todd Hitchins, 36, of Big Pine Key, about 30 miles east of Key West, said he planned to stock up on water and propane for his grill but wasn’t too worried.

“This will be good practice,” mused Hitchins, who said he’s lived here during much more powerful storms. “But you’ve got to be prepared, be ready.”

Jeff Emmett, operations manager at Fairfield Inn in Key West, said Saturday afternoon the hotel had no cancellations or early check-outs.

“Business as usual,” Emmett said. “Right now, we’re just keeping the guests informed.”

Chris Celestina, 24, was sitting at the hotel’s poolside bar while on vacation with four friends from Pennsylvania.

“We’re not really worried,” Celestina said as he ordered a drink. “Whatever happens, happens. If we get evacuated, that will definitely put a damper on our plans, but until we have to, we’re not moving.”

Some Keys residents were preparing for the aftermath.

Andrew Cardwell, 26, filled up nine 5-gallon gas cans for his employer, Pirate Scooter Rentals, early Saturday afternoon.

“As soon as the storm passes through, people are going to want to rent mopeds,” Cardwell said. “We’re just getting it while we can.”