Have you ever walked outside thinking it was one temperature but quickly discovered it felt colder? That is because of the "wind chill" effect. Wind chill is how cold people and animals feel when they are outside, not the actual temperature on the thermometer . It is based on how quickly your body loses heat when it is exposed to wind and cold. When the wind is strong, your body quickly loses heat, making the temperature of your skin drop. When scientists first started calculating wind chill, they used research conducted in 1945 by explorers to Antarctica who measured how quickly water froze outside. But water freezes faster than exposed skin, so the wind chill index based on that data wasn't accurate. In 2001, the US government began to measure wind chill more precisely by testing how quickly people's skin froze. Twelve volunteers were placed in a chilled wind tunnel. Equipment was stuck to their faces to measure the heat flow from their cheeks, forehead, nose and chin while they walked three miles per hour on a treadmill . The experiment revealed how quickly exposed skin can be damaged, particularly unprotected areas like your fingers, toes, the tip of your nose and your ear lobes. In fact, 40 percent of your body heat can be lost through your head! Signs you might have frostbite  are when the skin turns white or pale and you lose feeling in that area. The information collected from the volunteers helped scientists work out the math to compute wind chill. It involves wind speed and air temperature. If, for example, the temperature outside is zero degrees Fahrenheit and the wind is blowing at 15 miles per hour, the wind chill is calculated at 19 degrees below zero. At that wind chill temperature, exposed skin can freeze in 30 minutes. You can find a calculation table at www.nws.noaa.gov/om/windchill/index.shtml. Experts advise in cold weather that you wear loose-fitting, lightweight, warm clothing, worn on top of each other. Air caught between the clothes will keep you warm. The best cold-weather coats have head coverings made of woven material that keep out water. So next time the temperature drops and you want to play outside, listen to your parents when they tell you to wrap up warm! According to the text, wind chill   _  .
means how fast exposed skin freezes doesn't affect your head as much as other body parts changes according to the temperature on the thermometer changes from person to person depending on their health