If you check the weather app on your phone, you may see it’s currently 25°F, but “feels like” 15°F. This “feel like” temperature refers to the windchill, or how cold it feels when you’re out in cold weather with the wind blowing. The issue is the faster the wind blows, the more cold air moves across your skin’s surface and cools your skin’s temperature. Researchers at the National Weather Service (NWS) use a mathematical formula to calculate wind chill, and the whole thing is based on the speed of body heat loss in various temperatures. Some argue that the latest study on windchill only looked at 12 people, so scientists should instead rely on more complex metrics, such as the Universal Climate Index. Still, experts say you can use wind chill as a quick gauge for how much you should bundle up. And wind chill is significant, as it can cause you to develop frostbite quicker. To protect yourself from wind chill and frostbite, be sure to cover any exposed skin, including your face.