Summer may be almost a memory by now, but with the Labor Day weekend still ahead and given our long, warm, Washington autumns, at least one summer activity probably will be in full swing for a couple months - picnicking.

Just as thousands will head for distant country meadows to set up "groaning boards" on checkered tablecloths, so some of those picnickers later will spend one of the most miserable nights of their lives as victims of food poisoning.

Maybe the ham salad will get you. Or perhaps it will be the deviled eggs. Or that cream puff you leave out in the open for just a bit too long.

Whatever it is, the odds are it will not kill you. But according to Dr. Arthur Saz, chairman of the department of microbiology at Georgetown University Medical School, you won't "feel good enough to die while you" have food poisoning.

You will feel nauseous. You probably will vomit until you can vomit no longer. You may well have diarrhea.

"There are a lot of bacterial causes for food poisoning," says Saz, "and one of the most prevalent kind of food poisoning for picnickers is caused by a strain of staphylococcus called staphylococcus aureus."

The staphylococcus shows up in foods like custard, his salad, tuna salad and other dishes often containing mayonnaise, says Saz.

The bacterium is similar, if not identical, to that found in many boils and pimples, and for that reason he warns that anyone with boils and pimples should stay away from the food while it is being prepared.

"It causes an intoxication," or poisoning, he says, and the bacterium has to grow and multiply in the food to cause any damage. In order to grow, it needs warmth, and therein lies the key to avoiding food poisoning:

Make sure the food you take on a picnic is not allowed to stand out in the sun, or in a cooler that has lost its cool.

"Many people will take one of those chests and keep potato salad, or cream puffs, or what ever, in the chest," says Saz, "but then they get out in the field and the chest isn't cool any more. The salad comes out of the chest and then goes back in and the organisms start to grow. You're talking about then doubling every 10 minutes or so."

Once the multiplying organisms gets into the gastrointestinal tract it releases toxins, or poisons, which three to eight hours later often make the victim wish for a merciful death.

Another organism that causes much the same symptoms, says Saz, is bacillus cereus, which is often found in boiled rice allowed to stand unrefrigerated. "The organism reaches a resistant stage and then a lot of people take rice dishes on picnics."

Again, he says, proper handling of the food is the key to pleasant memories of the picnic. The rice should be placed in the refrigerator as soon as it's cooked and kept cool until it is eaten.

While most forms of food poisoning are self-limiting and will be gone by the next morning, there is at least one form which is far more serious - botulism.

Botuilism generally is found in canned foods, says Saz, who points out that this is the beginning of the canning season and a time when people may be likely to take along some home canned vegetables or fruits to spark up a gathering.

The organism is found in the soil, and if the produce being canned is not properly cooked - canned under pressure at a temperature of about 120 degrees centigrade - it can turn up in the canned food.

Botulism can turn up anywhere from one to eight days after the food has been eaten. Unlike the other food poisons, which cause stomach upsets, botulism causes paralysis, and in some cases includes of the repsiratory system - the victim may stop breathing.

About 25 percent of the victims of botulism die, says Saz, who adds that although there are antitoxins that can be administered, thre is not an awful lot that can be done for the victims of the bacterium.