Water, cool air and more water are the most important keys to surviving summer's savage heat, says George Washington University physiologist Richard A. Kenney. During hot weather, the body loses copious amounts of fluid that must be replaced to stave off muscle cramps, fainting and, in severe cases, death.

Outdoor sports, even for well-conditioned athletes, are not recommended during extremely hot and humid days, according to a number of health experts. But if you do spend extended periods in the heat, make sure to drink lots of liquids. Do not rely on your thirst trigger, Kenney warned. "Drink until your thirst is satisfied, then drink half again as much."

Kenney said sodas and beer do not cure dehydration. He explained that sugary drinks are slowly absorbed by the body and that the fizz quickly makes you feel full -- usually before your body has gotten enough liquid. Kenney said that alcohol causes an increased loss of water through the kidneys and that the carbohydrates in beer stimulate the body's furnace to burn those calories.

Heat and dehydration can lead to medical problems that can become life-threatening if not treated. Most people experience heat fatigue -- that weak, sluggish feeling after a walk or even a drive in the heat. The prescription: shade or air conditioning, if possible, and water, Kenney said. If this condition goes unchecked, the lack of fluid diminishes blood flow to the brain and can cause fainting.

Heat exhaustion is characterized by clammy skin, vomiting, cramps and dizziness. "Treat with cool air and large volumes of a lightly salted drink," Kenney said. He recommends one-half teaspoon of salt per quart. Alternatives such as Gatorade are suitable, but Kenney said this should be diluted with water because of the high sugar content.

Hyperthermia and the most serious stage -- heat stroke -- require immediate medical attention.

Small children and elderly people should be carefully monitored during hot weather. Each group is particularly susceptible to heat illness because their internal temperature regulators and sense of thirst are often inadequate, Kenney said.