Heat exhaustion and heat stroke are two different things, although they are commonly confused as the same condition. Heat exhaustion can occur anywhere there is poor air circulation, such as around an open furnace or heavy machinery, or even if the person is poorly adjusted to very warm temperatures. The body reacts by increasing the heart rate and strengthening blood circulation. Simple heat exhaustion can occur due to loss of body fluids and salts. The symptoms are usually excessive fatigue, dizziness and disorientation, normal skin temperature but a damp and clammy feeling.

To treat heat exhaustion, move to the victim to a cool spot and encourage drinking of cool water and rest.
Heat stroke is much more serious and occurs when the body's sweat glands have shut down. Some symptoms of heat stroke are mental confusion, collapse, unconsciousness, fever with dry, mottled skin. A heat stroke victim will die quickly, so don't wait for medical help to arrive--assist immediately.

The first thing you can do is move the victim to a cool place out of the sun and begin pouring cool water over the victim. Fan the victim to provide good air circulation until medical help arrives.