How to survive the heat:

* For starters, stay cool by taking it easy, wearing light-colored, loose-fitting clothes and drinking a lot of nonalcoholic beverages.Temperatures that trip the 100-degree mark can make you sick by overwhelming the body's ability to maintain a safe internal temperature.

Once your body temperature, normally 98.6 degrees, climbs above 104, your electrical system, enzymes and other biochemicals quit operating smoothly, warns Dr. Arthur L. Kellermann, chief of emergency medicine at the Regional Medical Center in Memphis.

Too much heat leads to two medical conditions, one more severe than the other:

* Heat exhaustion. Watch for drenching sweat, weakness and clammy skin.

Someone suffering heat exhaustion is usually still alert and aware of his surroundings, Kellermann said. Move the person immediately to a cool place and give him or her plenty of fluids, he said.

* Heat stroke. Beware of weakness, disorientation and skin that feels dry, but warm or hot. Those are signs the body's cooling system is collapsing, and the situation can be life-threatenng, Kellermann said.

Heat stroke requires an ambulance and immediate medical care.

"These people rarely perceive they're in trouble. They're not thinking clearly. They need to be brought in to the hospital over their objections," he said.

Keeping cool is especially important for the frail elderly, people working outside and lunch-hour joggers.

People without air conditioning or who are afraid to open their windows are especially vulnerable and need to be checked, he advised.

Special care is advised for those who take medicine for heart disease, high blood pressure, emphysema and psychiatric problems. Many of those drugs interfere with the body's ability to adapt to heat.

A heat wave is "one time when doctors won't argue with a little pinch of salt," he advises. Salt is vital to cell functions and is lost in sweat.