If you cause an animal to change its behavior, no matter how far away you are, you are in violation of park regulations. It results in the loss of coherence, shivering, loss of judgment, and unconsciousness. Stay dry to stay warm. Be prepared for the worst weather conditions. Hypothermia can strike during any time of the year in Yellowstone.
Avalanches kill people in the mountains every year.
Even a small snowslide could prove deadly if you are knocked unconscious. People have died when buried under less than a foot of snow. If you are working during the winter, an avalanche safety course is recommended. At least 19 people have died from falling into hot water in Yellowstone. Thin crust, especially in acid sulfate areas are subject to erosion and can easily collapse and are especially hazardous.