Extreme Heat: How the Human Body Reacts

Paris – 28.06.2026: At extremely high outdoor temperatures, the human body reacts with various mechanisms to regulate body temperature. A central process is vasodilation, in which the blood vessels expand to increase heat release. Additionally, the body begins to sweat to dissipate heat through evaporation. However, these adaptations are not without risks.

A common problem during extreme heat is dehydration. Through heavy sweating, the body loses not only water but also important minerals. A fluid loss of only two to three percent of body weight can significantly impair physical and mental performance. Symptoms of dehydration include dizziness, headaches, and general weakness.

Another risk is heat collapse, caused by a rapid drop in blood pressure due to expanded blood vessels. Affected individuals may experience symptoms such as dizziness, nausea, and consciousness disturbances. In such cases, it is important to bring the person into the shade, elevate their legs, and provide cooling.

With prolonged high temperatures, the body’s cooling mechanisms can become overloaded, potentially leading to heat stroke. This condition is life-threatening and is characterized by a body temperature above 40 degrees Celsius, hot dry skin, confusion, and a racing pulse. If heat stroke is suspected, emergency services must be called immediately, and the affected person should be cooled.

Those especially at risk are the elderly, children, and people with chronic illnesses. These groups should exercise particular caution on hot days and take regular breaks in cool rooms. It is recommended to consume sufficient fluids, preferably water or isotonic drinks, and to avoid physical exertion during the hottest parts of the day.

Furthermore, clothing during heat should be light, loose, and made of breathable materials to facilitate heat dissipation. Sun protection with hats, umbrellas, or protective clothing prevents additional heat stress. Air-conditioned rooms can provide relief but should not cause strong temperature fluctuations compared to the outdoor temperature in order to avoid circulatory problems.

Ambient temperature also influences sleep; high temperatures can cause sleep disturbances, which affect recovery and the immune system. Therefore, adequate fluid intake, a cool sleeping environment, and extended rest periods are essential.

In summary, it is crucial to take the body’s warning signs seriously and take timely measures to limit the health consequences of extreme heat. Targeted prevention can effectively reduce risks such as dehydration, heat collapse, and heat stroke.