Prolonged exposure in such conditions can lead to death, so if you must venture outside overnight, dress appropriately and do not leave any of your skin uncovered.
A winter storm warning has been posted for a large area of southwest Wyoming, including the cities of Rock Springs, Green River, Evanston and Pinedale.
Frostbite can occur in less than five minutes in such conditions, so dress appropriately if you go outside and take extra care to protect extremities such as fingers, toes, ear lobes and the tip of your nose.
The National Weather Service in Riverton has issued a * severe thunderstorm warning for... East Central Natrona County in Wyoming... * until 3:15 PM MDT *