At least once every winter, someone will repeat how you should wear a hat in cold weather because you lose 60% — or some other arbitrary number — of heat through your head. Is that actually true? Like a lot of things in life, it’s a trickier question than it seems. The origin of “losing heat through your head” is a vaguely scientific experiment conducted by the U.S. military in the 1950s, when subjects were dressed in cold weather survival suits designed to keep them warm, but not given hats. Under severe conditions like those of the study, people lose the most heat through their heads. Even though this study wasn’t about normally-dressed people wearing hats versus not wearing hats, people began repeating the “you lose heat through your head” myth. In the most basic terms, we lose heat based on how much of our body is covered. Since our head accounts for about 9% of our skin surface, we save about 9% of our body heat by wearing a hat. All of this is complicated by understanding that “losing heat” isn’t about how cold we ARE, but how cold we THINK we are. Just like the old saying “you’re only as old as you feel,” you’re only as cold as you feel. While you can feel less cold if you think warm thoughts and can physically acclimate to cold weather if you expose yourself to it, there are limits. When it’s cold, blood vessels in your arms and legs constrict and blood flows away from the fingers and toes to keep your brain and other organs warm. You’ll eventually get frostbite, even if you think warm thoughts. That physiological response might help explain why we feel like we should cover our heads. According to hypothermia experts, the face, head, and upper chest are up to five times as sensitive to changes in temperature as other areas of the body. Unless it's so cold that you'll get frostbite, whether you should or shouldn't wear a hat is a personal decision. The bottom line: if your head is cold, put a hat on.
