Heat stroke occurs when the body is exposed to an increase in temperature (over 40°C) combined with dehydration. It is caused by the body not being able to effectively control its temperature, usually from losing the ability to sweat. Heat stroke is an extremely serious condition which is often fatal, and can cause serious permanent injuries.
Overexertion (which raises the body temperature) combined with dehydration (which reduces the ability to sweat, which cools the body) is what would typically cause heat stroke associated with athletes and tradies, but heat stroke is more common in children and the elderly, and this is why it is vitally important to avoid leaving children in cars.
Experiments in the United States showed that the temperature inside a car can exceed 48oC when the outside temperature is only 21°C, even with the windows partially open. For this reason it is critically important not to leave children unattended in cars, but US figures show that 18% of all fatalities occur when the child has climbed into the car to play and been unable to get out, so parents and carers are advised to lock car doors when children are playing outside.
For active adults, the best advice is to avoid excess heat on hot days, and to ensure that you properly hydrate to ensure that the body can effectively reduce its heat. At UFS we can advise to the most effective rehydration processes.