Winter temperatures often hover near 0° F / -20° C throughout the day but may reach highs in the 20s / -5° C. Subzero over night temperatures are common. Occasionally, warm "chinook" winds will push daytime temperatures into the 40s / 5 - 10° C, causing significant melting of snowpack--especially at lower elevations. Yellowstone also typically experiences periods of bitterly cold weather. The lowest temperature recorded in Yellowstone was -66° F / -54° C near West Yellowstone on 09 Feb 1933. Annual snowfall averages near 150 inches / 380 cm in most of the park. At higher elevations, 200-400 inches / 5 - 10 meters of snowfall have been recorded. At any time of year, be prepared for sudden changes; unpredictability, more than anything else, characterizes Yellowstone's weather.
Snowmobilers and skiers should always check on temperatures and wind chill forecasts; subzero weather can make travel dangerous even with proper gear. Always carry extra clothing when hiking, skiing, or snowmobiling. Take advantage of the warming huts (heated shelters) provided in some park areas. Good walking shoes and layers of clothing are recommended throughout the year, but in the winter you'll also need warm boots. Cross-country skis or snowshoes are a 'must' in winter if you plan to go beyond the main roads and boardwalks.