Don't freeze your eggs!

During the 1940s, Paul A. Siple and and Charles F. Passel, renowned Antarctic explorers performed pioneering experiments that measured the time it took 250 grams of water to freeze in different temperature and wind conditions. A member of Admiral Byrd's first Antarctic expedition, Siple spent a total of six years performing research at the South Pole. It was on his third expedition that he and Passel conducted the experiments that resulted in the equation used to determine the wind chill index.

Simply put, the wind chill index is a measure of the cooling effect of wind. Heat is lost as cold air passes over exposed skin, evaporating the moisture on your skin and removing the insulating layer of air next to the body. As the air temperature drops or the wind speed increases, the rate of heat loss goes up. When the heat is lost faster than the body can replace it the danger of hypothermia and frostbite increases. Any movement of air past your body has the same cooling effect as wind, something to keep in mind when running, biking or skiing. You should also be aware that wet clothing has greatly reduced insulating capabilities and will result in body heat loss nearly equal to that of exposed flesh.

The wind chill index is best used as an indicator of how to dress for winter weather under various conditions. As we all know, it's important to wear several layers of lightweight clothing in order to maintain the insulating layer of warm air. At a minimum, shell garments should be wind-proof and water repellent. Mittens are are quite often warmer than gloves, and of course don't forget a hat.

The drawback to using the wind chill index is that it does not take in to account how well the person is dressed or the activity level. It also does not take into account the amount of heat lost through rapid breathing due to exertion. At wind speeds of 4 mph or less, the wind chill temperature is the same as the actual air temperature while wind speeds greater than 40 mph have little additional effect. Humidity also has very little cooling effect, particularly at low temperatures.