Heatstroke is a serious problem and the heatwaves that cause it, claim more lives on average than any other weather event in USA. While generally thought to affect the elderly and the very young, it can affect people of all ages, not just because of the heat in the environment (classic heatstroke) but also because of activity (exertional heatstroke). The problems caused by heatstroke sometimes happen but don't appear clinically, like GI ischemia.