Substances that inhibit cooling and cause dehydration such as alcohol, stimulants, medications, and age-related physiological changes predispose to so-called "classic" or non-exertional heat stroke (NEHS), most often in elderly and infirm individuals in summer situations with insufficient ventilation. Exertional heat stroke
Exertional heat stroke (EHS) can happen in young people without health problems or medications –  most often in athletes, outdoor laborers, or military personnel engaged in strenuous hot-weather activity or in first responders wearing heavy personal protective equipment. In environments that are not only hot but also humid, it is important to recognize that humidity reduces the degree to which the body can cool itself by perspiration and evaporation. For humans and other warm-blooded animals, excessive body temperature can disrupt enzymes regulating biochemical reactions that are essential for cellular respiration and the functioning of major organs. Cars
When the outside temperature is 21 °C (70 °F), the temperature inside a car parked in direct sunlight can quickly exceed 49 °C (120 °F). Young children or elderly adults left alone in a vehicle are at particular risk of succumbing to heat stroke. "Heat stroke in children and in the elderly can occur within minutes, even if a car window is opened slightly." As these groups of individuals may not be able to open car doors or to express discomfort verbally (or audibly, inside a closed car), their plight may not be immediately noticed by others in the vicinity.
Absorption is rapid and complete in most people but if the person is confused, unconscious, or unable to tolerate oral fluid, then an intravenous drip may be necessary for rehydration and electrolyte replacement.The persons condition should be reassessed and stabilized by trained medical personnel. The persons heart rate and breathing should be monitored, and cardiopulmonary resuscitation (CPR) may be necessary if the person goes into cardiac arrest. Prognosis
It was long believed that heat strokes lead only rarely to permanent deficits and that convalescence is almost complete. However, following the 1995 Chicago heat wave, researchers from the University of Chicago Medical Center studied all 58 patients with heat stroke severe enough to require intensive care at 12 area hospitals between July 12 and 20, 1995, ranging in age from 25 to 95 years. Nearly half of these patients died within a year –  21 percent before and 28 percent after release from the hospital. Many of the survivors had permanent loss of independent function; one-third had severe functional impairment at discharge, and none of them had improved after one year. The study also recognized that because of overcrowded conditions in all the participating hospitals during the crisis, the immediate care –  which is critical –  was not as comprehensive as it should have been.In rare cases, brain damage has been reported as a permanent sequela of severe heat stroke, most commonly cerebellar atrophy. Epidemiology
There are various aspects that can affect the incidence of heat stroke. Including sex, age, geographical location, and even occupation.