Heat exhaustion can occur if the body loses an excess amount of fluid through sweating and does not have it replenished. As your body becomes dehydrated, it begins to overheat and you may start to feel faint, dizzy, and lightheaded. If left untreated, heat exhaustion may progress to heat stroke, a life-threatening condition. At this stage, your temperature rises to a dangerous level and you may no longer sweat due to extreme dehydration. A person suffering from heat stroke may be in a state of confusion and disorientation. If you suspect someone is experiencing a heat stroke, call 911, get them out of the heat, and apply cold compresses on the body to lower body temperature quickly.