Pam Hixon prays for the hottest, heaviest, stickiest, most stifling weather that Atlanta can muster for this summer's Olympic Games. She prays for sunshine. She prays for humidity. No cool breezes please. No cloud cover.

After a grueling year training in Atlanta, members of the U.S. Women's Olympic field hockey team believe they have defeated their most formidable opponent in the Games, which begin July 19: the feared Georgia heat. Now they hope this summer gets scorching enough to melt the medal hopes of their opponents.

"The hotter the better," says Hixon, the team's coach.

The relentless Georgia heat with its 80 percent humidity and 90-degree days is likely to play a big role in determining winners and losers among the 10,000 athletes expected to compete at this summer's Games. Basketball players and gymnasts who perform in air-conditioned comfort don't have much to worry about. But the athletes who compete in the outdoor sports such as tennis, soccer, baseball, track and field, rowing and cycling must deal with the grueling weather. Many have been training in the Southeast United States to get their bodies acclimated.

Hot weather not only affects performance, it can also cause serious health problems, including death. As the date of the Olympics approaches, health officials are warning spectators as well as athletes to come prepared for the heat and humidity.

Over the past several years, between 2,000 and 3,000 athletes from Finland to Australia have come to the United States, armed with doctors, scientists and the latest cooling techniques that include humidity chambers and portable spray showers. Teams from more than 90 countries have practiced at 65 locations throughout Georgia, taking over small colleges and turning up at remote tracks. Finnish distance runners have sweated in Marietta. Swedish soccer players have gotten red-faced in Athens. Dutch softball players have practiced in LaGrange. The Russians arrived in Columbia, S.C. And the English have taken over Tallahassee, Fla.

"Our heat and humidity is the best in the U.S., something you don't normally sell," says Jeff Duke, a physical education administrator at Florida State University who has hosted British athletes in Tallahassee.

"I don't think people realize the extremities of {the heat in Atlanta} . . . the low energy level, the dizziness, pounding headaches and drenching sweat," said Kate Kauffman, a 21-year-old field hockey defender and member of the U.S. Olympic team. "If you haven't experienced it, you don't know what to expect." The Need to Acclimate

Atlanta is also entirely air-conditioned, which will create a double whammy for athletes who aren't used to the revolving-door shocks of a 68-degree room one minute and 90-degree outdoor temperature the next.

Athletes say the heat has totally changed their lifestyles, affecting their eating habits and even sleeping patterns as they try to make it no more bothersome than a stiff muscle. Some weigh every ounce of sweat. Some have calibrated secret water solutions for fighting dehydration. Water bottles are everywhere. And the words of the day both begin with H: "humidity" and "hydration."

"If you haven't acclimated, it will kill you," says Chris Huffins, 28, a decathlete from Berkeley, Calif., who is training at Life College outside Atlanta.

The body loses heat by radiating it directly into the atmosphere when the air around it is cooler than the skin. But the normal daily high of 87 in Atlanta is likely to be too hot to simply radiate heat, so the body will use another method to cool itself: sweating.

Sweating is controlled by the hypothalamic section of the brain, which acts like a thermostat for the human furnace. When the temperature is too hot for the body to radiate heat directly into the atmosphere, the hypothalamus sends a message to the sweat glands to increase production. When that sweat on the skin evaporates, it helps draw heat out of the body. But when the outside air is humid, as well as hot, the evaporation is less efficient.

These body mechanisms help prevent overheating, which can lead to organ failure, and, if not corrected, death. While sweating allows the body to rid itself of heat, it also causes the loss of fluids and electrolytes like sodium, potassium and chlorides, which are essential for cellular function throughout the body. Some of those electrolytes can be captured and reabsorbed back into the body before they evaporate from the surface of the skin, but others have to be replenished through solutions that athletes are constantly drinking. Those green Gatorade bottles are more than just props.

Training in the Georgia heat will help athletes accomplish several things: It will help them sweat more, and it will also increase production of a hormone called aldosterone that increases the reabsorption of electrolytes in the sweat glands, keeping the body on a more even keel. Living in the hot weather also helps athletes learn how much water they need to avoid dehydration without becoming waterlogged.

Making sure the body has the right amount of fluids is known as hydration, and it is critical to maintaining body temperature that keeps the athlete operating at maximum efficiency. Athletes are taught to drink water even when they aren't thirsty to replace fluids lost from sweat.

"If you're drinking water because you're thirsty, you're an hour too late," Huffins says.

The normal acclimatization process from a northern climate like Boston, Sweden or Germany to the hot tropics of Georgia takes from four to six weeks, according to Peter A. Kot, professor of physiology at Georgetown University Medical School.

By the end of six weeks, an athlete should increase sweat production from one liter per hour to something on the order of two or three liters per hour. The aldosterone should also help preserve electrolytes like salt. After a month, the athlete will lose only 3 to 5 grams of salt, compared with a loss of 15 to 30 grams for someone not adjusted to the heat, Kot said. Humidity Is a Serious Problem

But more than the heat, it's the overpowering humidity that has many athletes troubled. Atlanta's thick blanket of moisture in the air is so heavy that it creates a haze over the Southeast city. Breathing deeply can cause coughing. Afternoon showers produce steam. Hixon said she was stunned when her team walked into the Atlanta humidity one year ago.

"It was beyond my comprehension," says the Boston native. "It's like a sauna. The air just sits on your skin."

Since the humidity slows down the evaporation of sweat from the skin, it can turn off the cooling system of even the best-conditioned athletes. And when it gets that hot, says Kot, fans are not terribly effective because they simply circulate the same warm air around the body.

Athletes compensate for the humidity by drinking gallons of water often packed with electrolytes. They can also rest under umbrellas and occasionally seek relief from portable "Cloud Bursts," small shelters that contain misting sprays and offer temporary comfort from the heat. The Atlanta Committee for the Olympic Games has ordered at least 12 Cloud Bursts to be located around infields.

"The athletes are very worried about what's going to happen to the humidity," says Mike Spino, track coach at Life College, a chiropractic school outside Atlanta that has hosted hundreds of French, Italian, Australian, Swiss and Norwegian track and field athletes.

Spino said athletes have sat in humidity chambers to dehydrate themselves, measuring the amount they sweat to tell how much fluid intake they need. They have also taken part in extensive heat studies to determine how long it takes the aldosterone levels to increase. Some athletes even trained with thermometers in their rectums to determine how hot their inside temperature -- known as core temperature -- had risen, Spino said. The body must keep its core temperature around 98.6 degrees Fahrenheit to avoid fatigue, dizziness and organ problems.

"We found out anecdotally and in the study that northern Europeans have a tougher time than southern Europeans adjusting to the heat . . . ," Spino said. "Their core body temperature goes up real quick and their hydration drops."

Marathoner Risto Ulmala of Finland spent four weeks training in Atlanta during the past year and plans to head to southern Florida in late June to help adjust to the humidity. Ulmala, 33, said he drank so much water that he lost his appetite. And without food, he has no carbohydrates to fuel his long-distance runs.

Kauffman of the University of Maryland said she was drinking so much water that she ended up running to the bathroom every 15 minutes during the night. Some of her teammates got diarrhea and stopped eating.

But for some, the heat is their friend.

"My body works better in the humidity," said Huffins, whose decathlon competition calls for five hours a day exposure over two days in Olympic Stadium. "I feel looser, my muscles are more supple." He even has his own secret formula of water and electrolyte-filled sport drink to keep him hydrated.

"The sprinters tend to like it hot because it loosens up the muscles and they don't have to run far," said Derek Mills, a Georgia Tech graduate who is ranked third in the world in the 400-meter dash. Mills can rest in air-conditioned comfort and them pop out and compete in an event that lasts about a minute or two.

Others think that long-distance runners and some athletes in field events will be hurt because they will be under the sun longer and are more susceptible to dehydration.

"It will make people slower in the distance runs, 5,000 meter, 10,000 meter and marathon," said Alan Drosky, a track coach at Georgia Tech. "I would think the marathoners will have a tough time as well as the decathlon competitors. If I was sitting in my yard doing nothing for five hours, I'd be drained."

Hixon also believes the heat will be her friend and ally, and she has made it that way with a fine-tuned approach resembling something out of a Dallas Cowboy training manual. A battery of physiologists helped her measure how much her field hockey players moved during practices at Clark Atlanta University, where the Olympic competition will take place. Her scientists examined how quickly the players tired, when they needed to rest and when they went for drinks.

Result: a strategy of more substitutions.

"The biggest thing we looked at is how much weight did they lose during competition and how much did they need to rehydrate," Hixon said.

Any athlete loses weight because of sweat, but Hixon found that there is a threshold of around 2 percent of body weight that can't be crossed. She also determined how many pints of water each athlete needs to take in to replenish lost fluids. Every half-time now becomes a guzzling session so her players stay at their peak for all 70 minutes of competition.

The idea is to wear down the opponents mentally and physically. Hixon believes that many of the team's competitors from cooler climes may have unrealistic expectations of how much they can deal with the heat.

"If the conditions are nice, it's who is the better team," she said. "But if the humidity is high, with the mental game and being scientifically prepared . . . we think we can medal with this." Toughest Challenge May Be Faced By the Games' Fans

Call it the annual Siege of Atlanta.

Come June, a high-pressure weather system parks itself off the Atlantic Coast, sucking warm tropical air from the Gulf of Mexico into the Southeast.

For three months, this climatological oddity transforms the Georgia capital into a cauldron that locals call "Hotlanta." The average high temperature hovers around 80, but with the humidity it often pushes Atlantans to their breaking point. A walk to the car becomes a short-lived bath in the oozy mugginess.

"The humidity is incredible," said Bob Maxwell, a consultant to amusement parks. "I don't think we ever get used to it."

Into this broiler will step hundreds of thousands of people from across the world, visitors to the Olympic Games that start at the height of the heat: July 19 through Aug. 4.

If there's one thing that concerns Atlanta Olympic organizers, it's a heat wave that flattens the fans and instills them with memories of sweat instead of sports. Officials are caught between educating people on how to deal with the heat and not letting the subject overwhelm the Games.

"The heat in Atlanta has become a legend before the games have even started," said Susan Pease Langford, director of the city of Atlanta's office of Olympic coordination. "I think people will go away and have confirmed that it was hot, but . . . have a positive experience even in the heat."

Much has been made about the difficulties that the heat will pose for athletes, but health officials say they are more concerned about fans who are not used to the scorching sun and humidity. Olympic athletes, they point out, are in top physical shape and know every device and medical technique to reduce heat to a simple distraction. But it's a different story to the out-of-shape, overweight masses who aren't ready for a hostile climate.

"The biggest way you beat the heat is to be highly conditioned to the environment, and fans are not conditioned to this," said Jay Shoop, head of sports science at Georgia Tech and chief trainer for sports medicine within the Olympic Village.

"So many fans are not acclimatized, which means your body has not gotten used to the weather situation," Shoop said. "Many fans will be older and unconditioned, staying up late, partying and going out into the heat, walking long distances and strange places."

Heat wasn't a problem for the Los Angeles Games in 1984 because most people visited the events in the comfortable confines of their air-conditioned cars. But Atlanta is different. Many of the sites for the competition are clustered in a downtown area of central Atlanta, called the Olympic Ring. While some of these sites are very close to one another, others are a couple of miles apart. It's fine if the weather is 75 degrees and fair, but sauna-like conditions could make things very difficult for the unschooled visitor.

"If you're not accustomed to being outdoors for three hours at a stretch and walking half a mile, you're going to experience some kind of problem," said Laurie Olsen, a spokesman for the Atlanta Committee for the Olympic Games.

Olsen calls the committee's heat defense "the Cadillac of programs." Advice on how to deal with the heat is being mailed to each ticket buyer, stressing the importance of wearing loose-fitting cotton (a sweat absorber) along with the benefits of hydration (drink lots of water) and wide-brimmed hats. Several competition sites are air conditioned, and many of the outdoor stadiums have shaded areas and misty water sprays to offer temporary comfort to fans suffering in sun-drenched seats. Spectators can bring in their own water bottles or bottled water will be on sale for $4 a liter, hand-held spray misters will be available as well as hats, sunscreen, sunglasses and fans. Air-conditioned tents with television sets will also be present at several outdoor competition sites.

Each site will have a heat coordinator and medical volunteers roaming the facility to look for people suffering from discomfort and offering sunscreen to those getting overexposed, according to Atlanta organizers.

Organizers are quick to point out that indoors Atlanta is virtually 100 percent air conditioned compared to 20 percent in Barcelona where the summer Olympic games were held in 1992. That means hotels, restaurants, T-shirt shops and malls can offer relief -- but in some places the cost is significant.

Coca-Cola's Olympic City, for example, is a recreation center. It will offer Coca-Cola stands, a food court and so-called chilly tents that offer T-shirts and a turn in high-tech simulators that allow one to pitch to Detroit Tigers first-baseman Cecil Fielder or try to hit off Braves pitcher Tom Glavine. Price of admission: $13 per adult. Bottles of Coke cost $2.

For those trudging the streets, the city of Atlanta is erecting eight tents at high-traffic sites to provide water, shade and helpful tips to travelers. Several churches will also open their doors for people to come in and rest, said Langford.

Atlanta's Olympic Committee will also have toilet facilities and drinking water at depots throughout the metropolitan area, where fans can pick up trains or shuttles to the Games.

In addition, hundreds of vending carts, tents and kiosks are being set up throughout the city and in parking lots. Empty storefronts are turning into beer gardens and guest stops selling sun block and lemonade.

Shoop said Atlanta's heat has more staying power that a lot of other muggy cities: it starts earlier in the morning and lasts longer into the evening.

During the winter months, Atlanta gets cool, sometimes stormy, air from the jet stream that travels from west to east across the northern part of the continent. The moisture-laden jet stream is about 100 miles wide and is 30,000 feet high, and it tends to swoop down into the Southeast, bringing storms and cooler air to the region.

But in the summer, the jet stream stays north and misses Georgia. That leaves a vacuum in the weather pattern that is filled by a high-pressure system that creeps up from the Gulf of Mexico and rests above the Atlantic Ocean off the coast of Georgia. Air flows up into the United States from the Atlantic and the Gulf of Mexico. The result is a tropical atmosphere over the Southeast. "The air has been blowing over the open water for long periods of time, and that brings us our humidity," said Kent McMullen, lead forecaster for the National Weather Service in Peachtree City, south of Atlanta. "It's just one of those climatological things."

The humidity becomes so thick that a gray haze settles over the area. Afternoon thunderstorms cool the air for an hour, but the humidity snaps right back and the heat sets in again.

The normal daily high in July is 88, while the minimum is 69. The July monthly average is 78 degrees. The average humidity reaches its peak at about 7 p.m., when it hits 66 percent. About 60 percent of the average July sky is covered by clouds, according to the Weather Service.

Experts say the best relief is to head for the air conditioning, but some Atlantans go one better: they head for the North or the West for vacations. Others have learned to live with it. Joan Hicks of the Atlanta Braves baseball team's front office has her own, low-tech solution. And it doesn't involve going anywhere.

"You just suck it up, drink some water and sit under a tree somewhere," she said. CAPTION: At its best, summer weather encourages us to get outdoors in the fresh air and enjoy any of a broad range of activities, from basking on the beach to hiking in the hills. But at its worst, summertime heat and humidity is not only unpleasant, it can pose a serious -- even life-threatening -- health risk.

The U.S. Centers for Disease Control and Prevention says exposure to extreme temperatures causes hundreds of deaths annually during years in which there is no heat wave. As recently as 1980, 1,700 deaths nationwide were directly attributed to heat exposure. HEAT-RELATED DEATHS PER 1 MILLION POPULATION, BY AGE GROUP (This chart was not available) COOL TIPS - Stay indoors as much as possible, especially in well-ventilated or air conditioned areas. - If you must be outside, stay in the shade or wear a hat. Avoid hot surfaces, such as asphalt or pavement, which tend to absorb heat. - Avoid strenuous activity, particularly around midday. Slow down. Cut back on exercise and outdoor tasks. Schedule workouts in early morning or evening, if possible. Stop physical activities at the first signs of fatigue, light-headedness or sweltering. - Never leave a child or pet in a vehicle with the windows shut tight, because the temperature inside can soar quickly to a deadly level. - Wear loose-fitting, lightweight and light-colored clothing. Choose fibers of natural fabrics, such as cotton or silk, which help the body release heat. - Drink plenty of water or other nonalcoholic beverages. Avoid alcohol and caffeine, which can interfere with sweating and cause the body to lose fluids. - Do not take salt tablets unless directed to do so by a doctor. - Take cool or tepid showers or baths, since water conducts heat away from the body faster than air does. - Simplify meals to shorten cooking time. Bake early in the day if possible. Use a microwave rather than a range to cut down on kitchen heat. - Eat light. Salads and fruit help replenish fluids and increase the body's metabolic rate less than meats. - Use air conditioning efficiently. If you have window units rather than central air conditioning, keep one or two rooms cool and closed off rather than trying to cool the entire home. Make sure thermostats are turned off or set low. - If your home is not air-conditioned, use fans to circulate air. Also consider spending part of the day in a public building with air conditioning, such as a library, movie theater, museum or indoor shopping mall. CAPTION: Jackie Joyner-Kersee rests in the Atlanta heat last month. CAPTION: At Coca-Cola's Olympic City, 10-year-old Steven Bailey of Stockbridge, Ga., enjoys the refreshing mist from a giant bottle that sprays anyone whose face is in the right spot. CAPTION: In August 1995, Tulipan Neopol kept cool with fans after a freestyle event that will be in the 1996 Olympics for the first time.