MIAMI -- Oil from the massive Gulf of Mexico spill has as high as an 80 percent chance of reaching the Florida Keys and Miami, according to a computer model released Friday by the federal government.

The model, released by the National Oceanic and Atmospheric Administration, shows Florida's southeastern coast has a 61 percent to 80 percent chance of seeing oil by Aug. 18. The area from the Keys north to the Fort Lauderdale area could see sheen, tar balls or other oil remnants within 20 miles of the coastline.

Outside those areas and the Florida Panhandle, which has already seen beaches littered with tar balls, other parts of the state show a low probability of oil. The state's western coast has a 20 percent chance or lower of seeing oil.

Parts of southwest Florida have less than a 1 percent chance, according to the model, which assumes oil will continue to seep from the site of the April 20 explosion on the drilling rig Deepwater Horizon.

Rachel Wilhelm, a spokeswoman for NOAA, said the amount of oil seen in South Florida could range widely. However, at least at first, it will likely be heavily weathered remnants.

"We're talking about light sheens and streamers and tar balls perhaps the size of dime to maybe the size of your fist," Wilhelm said. "Certainly not what you're seeing in the Gulf right now -- we're talking about very weathered, highly dispersed oil."

Meanwhile, across the oil-stained Gulf Coast, it's going to be a glum Fourth of July.

The stakes are high for the hotels, motels, restaurants, souvenir shops and ice cream stands along the beaches of what is affectionately known as the Redneck Riviera.

"The Fourth of July is a key, key component," said Chris Thompson, president and CEO of Visit Florida, which promotes tourism in the state. "It's one of the most critical weekends," when many businesses make the bulk of their summer tourism income.

Tourism officials say there have been numerous hotel cancellations across the coast. About 25 percent of all rooms in the Pensacola Bay area were still vacant on Friday, said Ed Schroeder, director of the convention and visitors bureau. Last year, hotel occupancy was 100 percent at the start of the holiday weekend.

The oil spill will probably ruin the holiday for Kenny DiNero, who runs a dockside bait and tackle shop in Ocean Springs, Miss. Normally on the Fourth, the waters off Mississippi are full of boats. People fish and stop on islands to swim and have cookouts.

This year, "all the islands are closed because of the spill. There won't be any fuel sold. There won't be any ice sold. There won't be any bait sold. And there won't be any damn fishing," DiNero said. "Normally on the Fourth I do $10,000 to $15,000 in sales. This weekend I'll be lucky to do $500."

Many businesses are fighting the misperception that every stretch of beach is coated in oil.

Pensacola Beach is doing its best to make its sands presentable. About 1,300 BP employees and county crews are working overnight to clean whatever oil washes up during high tide. By most mornings, the tourist sections are largely clean, with only orange and brown stains in the sand left behind.

Visitors like Laura Barbier of Dallas said they have been pleasantly surprised. She said her family has been visiting the Gulf Coast every summer for 15 years. They almost didn't come this year because of the oil.

"I'm glad we did," she said, stepping on a gooey tar ball that rolled in with a wave. "It's not as bad as the news made it sound."