Make sure at least one person in your group has had first aid training, knows beforehand the contents and use of the kit, or has equivalent knowledge of how to deal with injuries. Heat exhaustion, which can afflict individuals in excellent physical condition, is caused by prolonged physical exertion in a hot environment. Cool the victim down by whatever means available. Ignoring cold or wet conditions and letting your body's core temperature drop can be a life threatening situation. Without treatment, the decline in body temperature can lead to stupor, collapse, and death.
Prevention is the best treatment.
Symptoms include shivering, slurred speech, memory lapses, fumbling hands, and drowsiness. Treatment includes getting the victim out of the weather, removing wet clothes and replacing them with dry ones. Build a fire for additional warmth and give the person warm drinks. If victim is semiconscious, or worse, try to keep him awake. Put him into a sleeping bag with another person.