As much as people enjoy the warm summer months, high temperatures can be hard on the human body. “As mammals, we live close to the thermal edge of life and death,” says Craig Heller, a physiologist and biology professor at Stanford University. “We run at 37°C [98.6°F], and only a couple of degrees above that puts us into heat illness and heat stroke.” Not every part of the body is the same temperature, however, “and blood flow determines where the heat is distributed,” Heller says. [time-brightcove not-tgx=”true”] What part of the body cools down the fastest?