Check out this link for a great chart, information on what it means, and at the bottom of the page, an actual calculation plug in the numbers tool.
http://www.nws.noaa.gov/om/windchill/index.shtml
Before heading out, follow safety measures, including layering clothing, full face covering, sunglasses, lip balm. Leave your itinerary with a friend or in your vehicle.
Wind chill can kill.
