Hurricane Wilma, a Category 4 storm, regained strength this afternoon, meteorologists warned, and it was expected to barrel into the Yucatan Peninsula sometime Friday and then veer east toward Florida.

Tourists in the Yucatan scrambled to get flights home or find shelter. Florida Gov. Jeb Bush declared a state of emergency ahead of the storm while hurricane-weary Floridians boarded up windows, filled their cars with gas and flocked to supermarkets to stock up on supplies. The declaration gives officials the ability to activate the National Guard and broad authority over evacuation plans and the distribution of recovery supplies and other items.

Wilma, churning winds of 145 mph with higher gusts, was about 135 miles southeast of the Mexican island beach resort of Cozumel, lumbering at 6 mph toward the Yucatan Peninsula, according to a 5 p.m. EDT advisory issued by the National Hurricane Center in Miami. Winds and big waves battered the white sand beaches of popular Mexican resorts Cancun and Cozumel ahead of the hurricane.

The center said Wilma could continue to strengthen over the next 24 hours and may regain its Category 5 level winds of 156 mph or more as it approaches the Yucatan. But the forecast also noted that the newest computer models suggest Wilma will spend longer battering the Yucatan than previously thought, which would leave it weakened as it heads to Florida.

Storm surges of up to 11 feet above normal tide levels are expected near where the "center makes landfall on the Yucatan peninsula," the advisory said.

Max Mayfield, director of the hurricane center, said the storm will most likely approach Florida weaker than a Category 4, but he said it would still be a dangerous system. "Even a Category 2 or 1 can have big consequences here," he told reporters at a late afternoon briefing.

The storm is expected to hover near or over the Yucatan for the next two days, dumping more than a foot of rain there, before it makes a sharp right toward the Florida coast, where forecasters predict it will make landfall in the southeastern part of the state sometime late Sunday, more than a day later than first predicted.

Mayfield said most of the computer models have the storm taking a turn toward the Florida coast after it enters the Gulf of Mexico. The models vary, however, on the hurricane's intensity, speed and exactly where it might touch down.

He predicted Florida could suffer a tremendous impact from the storm. Florida officials ordered the evacuation yesterday of tourists and people living in trailers and recreational vehicles from the low-lying Florida Keys, and further evacuation orders are expected.

"All interests in the Florida Keys and the Florida peninsula should closely monitor the progress of extremely dangerous Hurricane Wilma," the latest hurricane center advisory said.

FEMA's acting director, R. David Paulison, recommended that Floridians stock three days of food and water, medicine, flashlights and extra batteries, as well as fill their vehicles with gas to get prepared for the storm. He said that if an evacuation is ordered, residents should make sure they bring important documents with them, such as bank statements, checkbooks, birth certificates, insurance certificates and credit cards.

He insisted that FEMA, which was roundly criticized for being unprepared for Hurricane Katrina, is ready now. "We are going to do very well with this hurricane," Paulison said at a news conference at FEMA headquarters in Washington. "This is going to be a good response."

The hurricane was already causing problems for sporting events scheduled for this weekend in Florida. The Miami Dolphins announced that their game against the Kansas City Chiefs, originally scheduled for Sunday, will now be played at 7 p.m. Friday. It's the third time since the start of the 2004 season that the Dolphins have rescheduled a home game because of an impending hurricane.

Hurricane force winds extend outward up to 85 miles from the hurricane's eye, the advisory said. Hurricane watches were in effect for much of the Yucatan and parts of Cuba, where more than two feet of rain are predicted in some parts of the country. Tropical storm warnings were in effect for Belize and parts of Honduras.

At one point yesterday, Wilma became the most intense storm on record when its barometric pressure dropped to 882 millibars. Hurricane Katrina, which devastated the Gulf Coast, was measured at 902 millibars at its peak strength.

The lower a storm's pressure, the stronger its winds. By the latest advisory, the storm's pressure had risen to 918 millibars.

Wilma also made history yesterday as the most rapidly strengthening storm on record after it grew from a tropical storm to a Category 5 hurricane in less than 24 hours.

Wilma is the 12th hurricane of the six-month season and the 21st named storm of the year in the Atlantic Ocean. Any further storms would be named after the Greek alphabet, starting with Alpha. The hurricane season ends Nov. 30.