[Heat stroke on the hottest day of the year].

Heat stroke is the most extreme form of heat-related illness. An imbalance between excessive body heat production and inadequate compensatory mechanisms can lead to multi-organ failure and even death. There are two types of heat stroke: exertional heat stroke and non-exertional (a.k.a. classical) heat stroke. In exertional heat stroke, extreme physical activity leads to overheating of the body, whereas classical heat stroke is usually caused by a hot environment without adequate thermoregulation. We present a case of classical heat stroke in an elderly patient. Since we are faced with an aging population in combination with an increase in heat waves as a consequence of climate change, increasing numbers of elderly people are expected to be at risk of heat stroke. Prevention and effective cooling by first responders are crucial for a better prognosis.