The human body is amazing, but it has limits when it comes to heat. The average person can survive in temperatures up to about 107°F to 108°F (42°C) for a short time.
If the core body temperature goes higher than that, the brain and organs start to fail. Death can occur if the core temperature reaches 111°F (44°C).
When we are exposed to heat, the body tries to cool itself by sweating and increasing blood flow to the skin. But in extreme heat, especially if the air is also very humid, this system can fail.
In a dry environment, people can survive temperatures as high as 120°F (49°C) or even more for a short time—as long as they stay hydrated and avoid physical activity.
However, in saunas, temperatures can reach 180°F (82°C) or higher. Some people can stay in a sauna for several minutes because the dry air makes it easier for sweat to evaporate.
Still, the real danger is when the body cannot cool down fast enough. This leads to heat exhaustion or heatstroke, which can be fatal.
In special situations, like for firefighters or athletes, the body can be trained to handle more heat, but there are still limits.
Children, elderly people, and those with health problems are at greater risk in hot environments.