Weather conditions may cause icy trails, deep snow, or barren sections increasing the difficulty of a trail. When skiing near thermal areas, stay on marked trails. Approaching thermal features is dangerous because of unstable ground. The snow in these areas is often icy and what appears to be bare ground may be a thin crust over boiling water. Winter weather in Yellowstone changes rapidly and can be severe.
Many areas are frequently windy.
Wear proper clothing. Watch yourself and other members of your party for signs of frostbite and hypothermia. For your safety, always ski with someone else. Carry extra clothing, food, water, map and compass, matches, flashlight, and a whistle. Sign in at trail registers and tell someone where you are going, by what route, and when you plan to return.