Heat stroke is a form of hyperthermia in which the body temperature is elevated dramatically. Heat stroke is a medical emergency and can be fatal if not promptly and properly treated. The cause of heat stroke is an elevation in body temperature, often accompanied by dehydration. Symptoms of heat stroke can include confusion, agitation, disorientation, the absence of sweating, and. coma. Heat stroke is diagnosed by observation of the symptoms and signs in a person exposed to extreme temperatures.