Winter in Yellowstone ranges in temperature from the high twenties and thirties durring the day, to sub-zero temperatures at night. The record low temperature is -66F. The park averages 150 inches of snow a year, but higher elevations can receive over twice that amount.
Spring in Yellowstone means temperatures ranging from the 30s to the 60s with overnight lows in the teens and single didgits. Snow is common, and often can leave over a foot in a 24 hour period.
Daytime temperatures in the summer stay mostly in the 70s, with some climbs into the 80s. At night, temperatures can drop quickly to freezing levels in higher elevations, and thunderstorms are common in the afternoons.
Fall in Yellowstone is very similar to spring, except weather fluctuations tend to be a little less severe. Be prepared at any time for rain and snow. BAckcountry campers should be aware that temperatures can drop into the single digits.