Yellowstone is a land of extremes; from water that is boiling at the surface to one of the coldest climates in the country. Climate helps determine all we see across this high-mountain landscape. Most winters in the park, the thermometers dip well below 0 degrees F for extended periods.
On one such cold spell in 1933, the temperature at Riverside Station, near the park’s west gate, dropped to -66 degrees F; nearly 100 degrees below the freezing point. While that is a record for Yellowstone, it is not a national record; the record for the contiguous United States came on January 20, 1954. On that day, at Rogers Pass, Montana, the temperature dropped to -70 degrees F.
Even short periods at those low temperatures can have an effect on native species. For instance, the pine-bark beetle and the spruce-bud worm can both kill a forest, but extreme cold spells can keep these insects in check.
Cold spells also help determine where we find species like fish. During longer periods of cold, ice can begin to form on river and streambeds. Called anchor-ice for the way it attaches to rocks near the bottom, it is one of the first steps toward a completely frozen streambed, which eliminates fish.
Other habitats are also a direct result of Yellowstone’s winter. When the park gets covered by a deep blanket of snow, many rodents and insects use the layer between the ground and the snow as a place to survive the winter. If snow is deep enough, the temperature at ground level is at or near 32 degrees F.
Yellowstone’s cold climate helps to keep the wilderness pristine; cold air is heavier than warmer air and creates an area of high pressure. Winds flow from high pressure to low pressure; this means most local winds are flowing off of the Yellowstone plateau, which helps to keep airborne pollutants like fertilizers out of the park.