Explanation:

eat stroke is the most severe form and is defined as a body temperature higher than 41.1°C (106°F) associated with neurological (brain) dysfunction
Heat stroke occurs when thermoregulation is overwhelmed by a combination of excessive metabolic production of heat (exertion), excessive environmental heat, and insufficient or impaired heat loss, resulting in an abnormally high body temperature.
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 (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 certified 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.
The body normally generates heat as a result of metabolism, and is usually able to dissipate the heat by radiation of heat through the skin or by evaporation of sweat. However, in extreme heat, high humidity, or vigorous physical exertion under the sun, the body may not be able to sufficiently dissipate the heat and the body temperature rises, sometimes up to 106 F (41.1 C) or higher. Another cause of heat stroke is dehydration. A dehydrated person may not be able to sweat fast enough to dissipate heat, which causes the body temperature to rise.
Heat stroke is not the same as a stroke. "Stroke" is the general term used to describe decreased oxygen flow to an area of the brain.
http://indianexpress.com/article/lifestyle/health/why-people-die-of-heat-stroke-all-you-need-to-know-about-the-illness/h