Yellowstone National Park
Long before any recorded human history in Yellowstone, a massive volcanic eruption spewed an immense volume of ash that covered all of the western U.S., much of the Midwest, northern Mexico and some areas of the eastern Pacific. The eruption dwarfed that of Mt. St. Helens in 1980 and left a caldera 30 miles wide by 45 miles long. That climactic event occurred about 640,000 years ago, and was one of many processes that shaped Yellowstone National Park--a region once rumored to be the place where hell bubbles up. Geothermal wonders, such as Old Faithful, are evidence of one of the world's largest active volcanoes. These spectacular features bemused and befuddled the park's earliest visitors, and helped lead to the creation of the world's first national park. Fur trappers' fantastic tales of cauldrons of bubbling mud and roaring geysers sending steaming plumes skyward made their way back east.
Several expeditions were sent to investigate, opening the West to further exploration and exploitation. In 1871, Ferdinand Hayden led an expedition that included artist Thomas Moran and photographer William H. Jackson. They brought back images that helped convince Congress that the area known as Yellowstone needed to be protected and preserved. In 1872, President Ulysses S. Grant signed a law declaring that Yellowstone would forever be dedicated and set apart as a public park or pleasuring ground for the benefit and enjoyment of the people.
Seasonality / Weather
Summer: Daytime temperatures are often in the 70s (25C) and occasionally in the 80s (30C) in lower elevations. Nights are usually cool and temperatures may drop below freezing at higher elevations. Thunderstorms are common in the afternoons.
Winter: Temperatures often range from zero to 20F(-20 to -5C) throughout the day. Sub-zero temperatures over-night are common. The record low temperature is -66F (-54C). Snowfall is highly variable. While the average is 150 inches per year, it is not uncommon for higher elevations to get twice that amount. See Winter Daily Reports.
Spring & Fall: Daytime temperatures range from the 30s to the 60s (0 to 20C) with overnight lows in the teens to single digits (-5 to -20C). Snow is common in the Spring and Fall with regular accumulations of 12" in a 24 hour period. At any time of year, be prepared for sudden changes. Unpredictability, more than anything else, characterizes Yellowstone's weather. Always be equipped with a wide range of clothing options. Be sure to bring a warm jacket and rain gear even in the summer.
North Entrance - Near the gateway community of Gardiner, MT, the North Entrance is the only park entrance open to wheeled vehicles all year. November through April, the North Entrance provides the only access to Cooke City, MT. Beyond Cooke City the road is closed to wheeled vehicles November through April. The road from Mammoth to Norris is open to wheeled vehicles from the third Friday in April through the first Sunday in November, and to tracked oversnow vehicles from the third Wednesday in December to Monday of the first full week in March.
West Entrance - Adjacent to the town of West Yellowstone, MT, the West Entrance is open to wheeled vehicles from the third Friday in April through the first Sunday in November, and to tracked oversnow vehicles from
Bus service from Bozeman, MT to West Yellowstone, MT via Highway 191 is available all year. Bus service directly from Idaho to West Yellowstone is limited to the summer months. Commercial transportation from Bozeman, MT to Gardiner, MT is available during the winter and summer seasons. Commercial transportation to the park from Cody and Jackson, WY is available during the summer season. Contact local Chambers of Commerce for specific carriers and schedules.
Train service is not available to Yellowstone National Park. The nearest train depots are in southeast Idaho, Salt Lake City, Utah and northern Montana. Contact Amtrak for specific schedules.