Scientists have developed an index that will let you know if the combination of cold temperature and winds are a danger to humans. This is called the Wind Chill Index.
Wind chill numbers lower than -18° F are very dangerous, because a person’s skin can become frozen within 30 minutes or less. Frozen skin is sometimes called frostbite.
A temperature of -5° F with a wind speed of 30 miles per hour creates a wind chill of -32° F. At this wind chill, frostbite would occur within 10 minutes.