The human body’s temperature rises over the course of the marathon. Even after completing the race, marathoners continue to shed heat. But if the conditions are cold, they could lose that heat too rapidly and run the risk of hypothermia, a dangerous drop in core body temperature.
“Your body is still trying to get rid of that extra heat, even though it’s colder outside,” said Dr. Alexis Colvin, an orthopedic surgeon specializing in sports medicine at Mount Sinai Hospital. “You can become hypothermic if your body hasn’t quite re-established the balance between getting rid of the heat and keeping the heat in.”