Hurricane Emily weakened slightly as it began lashing the beaches of the Yucatan peninsula (search) on Sunday, hours after thousands of jittery tourists streamed out of their waterfront hotels and fled inland to shelter at schools and gymnasiums.

The Category 4 storm caused heavy flooding that swept four people to their deaths in Jamaica on Saturday. In Mexico, it downed signs, toppled trees and whipped white sands from the beaches in Cancun (search).

Two people also were killed in a helicopter crash in the Gulf of Mexico (search) as more than 15,500 workers were evacuated from offshore oil platforms, raising to seven the number of people killed in the second major hurricane of the Atlantic season.

Click here to track Hurricane Emily.

Emily's winds decreased from 145 mph to 135 mph as it bore down on the peninsula Sunday evening and would likely weaken further as it headed toward the Gulf, according to the U.S. National Hurricane Center.

Emily was likely to make landfall again on Wednesday anywhere from northeastern Mexico to southern Texas, said Jack Beven, the hurricane specialist at the Miami-based center said. He cautioned it was too early to make a precise prediction.

In Cancun, hundreds of buses moved 30,000 tourists to temporary shelters, part of the 70,000 to 80,000 people being evacuated statewide from resorts like Tulum, Playa de Carmen and Cozumel. Cancun's airport closed Sunday afternoon after thousands lined up at ticket counters, trying to get flights out before the storm hit.

By late afternoon, heavy winds tugged at palm trees and sent the last people at the beach running for their cars.

Christopher Espinoza of Cancun braved howling bursts of wind to look out over the pounding surf. "The waves are already starting to take away part of the beach," he said.

Erosion has long been a problem for Cancun, and waves were starting to lap almost at the doorsteps of some hotels.

Hundreds of mostly foreign tourists lay shoulder-to-shoulder on thin foam pads in a sweltering gymnasium near the center of Cancun, one of Mexico's most popular tourist destinations known for its white-sand beaches, sprawling hotel complexes and all-night discos.

The evacuees were given free bottled water and sandwiches, but many gasped when a hard rain rattled the metal roof of the building. Some asked how long they would have to remain.

"It's hot in here," said Beth McGhee, 46, a tourist from Independence, Mo. "We feel like we've been kept in the dark until this morning. But we're safe, and that's what's important."

Cancun's grim-faced mayor, Francisco Alor, said the city was preparing for a near-direct hit by Emily.

"This hurricane is coming with the same force as Gilbert," he said referring to a notorious 1988 hurricane that killed 300 people in Mexico and the Caribbean.

The city's last big evacuation was for Gilbert. But in 1988, the city and surrounding resort areas had only about 8,000 hotel rooms. That number has since grown to over 50,000.

Tourism and hotel officials had said guests of beachside hotels would be relocated to ballrooms and convention centers in larger, well-protected hotels, but the first wave of evacuees was ferried to gymnasiums and government schools.

In Jamaica, torrential rains drenched the south coast and washed away at least three houses, while a man, a woman, an infant boy and his 5-year-old sister were swept away in a car Saturday night. Searchers on Sunday found the four bodies trapped inside the car, which was filled with mud and other debris, police said.

The family had been driving through a flooded rural road in southwest Jamaica when a surge of water pushed them over a cliff.

The Cayman Islands escaped major damage Saturday. The islands and a handful of other Caribbean countries were devastated last year when three catastrophic hurricanes — Frances, Ivan and Jeanne — tore through the region with a collective ferocity not seen in years, causing hundreds of deaths and billions of dollars in damage.

On Sunday evening, the center of the storm was about 90 miles southeast of Cozumel, an island just south of Cancun, and was approaching the peninsula at about 20 mph.

Tourists in Cozumel also were moved to more central accommodations and local residents prepared to flee their homes for shelters in schools and communities on the island.

President Vicente Fox encouraged peninsula residents to seek shelter and not worry about leaving property and possessions unguarded.

State oil company Pemex was removing the last few hundred workers from oil platforms on the Gulf of Mexico. Strong winds downed a helicopter participating in the evacuation on Saturday night, killing a pilot and co-pilot, the company said.

The platform evacuations closed 63 wells and halting the production of 480,000 barrels of oil per day.

Emily has unleashed heavy surf, gusty winds and torrential rains across the Caribbean, hitting hard Thursday at Grenada, where at least one man was killed when his home was buried under a landslide.

The storm trailed Hurricane Dennis, which killed at least 25 people in Haiti and 16 in Cuba earlier this month.

Forecasters have predicted up to 15 Atlantic tropical storms this year, including three to five major hurricanes. The hurricane season began June 1 and runs through Nov. 30.