The human body can’t handle excessive heat. The processes that keep us alive work best within a certain temperature window. That’s generally between about 36° and 37° Celsius (96.8° to 98.6° Fahrenheit), depending on the person.
If someone’s core body temperature goes higher, “the body’s primary response to heat is to try and get rid of it,” explains Jonathan Samet. He’s the dean of the Colorado School of Public Health in Aurora. To get rid of excess heat, blood vessels in the skin dilate, or expand. At the same time, the heart begins beating faster. That pushes blood flow to the skin. There, the blood can release heat to cool down. Meanwhile, sweating kicks in to cool the skin.