Yellowstone National Park in northwestern Wyoming and adjoining Montana and Idaho represents the glorious heart of the Greater Yellowstone Ecosystem, a tremendous wilderness mosaic in the Middle Rocky Mountains. Few national parks in the world combine the history, geological splendor and ecosystem scale of Yellowstone, which set the standard in 1872. Visitors in mid-August can participate in the full spectrum of the park’s experience: from the hubbub of Mammoth and Canyon to the wild solitude of an Absaroka Range saddle or a lodgepole pine forest miles from the nearest road.
August's weather conditions are typically among the most pleasant of the Yellowstone year. Daytime temperatures are usually warm; the average maximum for an August day is about 78 degrees Fahrenheit, and it may occasionally be even hotter, particularly in the lower elevations of the Northern Range. The average nighttime low for the month is about 45 degrees. Much colder temperatures are possible, however; Yellowstone is high enough in elevation that the mercury can plunge below freezing any time of year. Afternoon and early evening dry thunderstorms are common this season, so hikers should stay aware of prevailing conditions. On many Yellowstone trails, it's easy to be caught exposed to lightning in a wildfire-scorched ghost forest, open sagebrush foothills or the high country.
By August, much of the park -- the higher elevations of which are snowbound most of the year -- is usually accessible. Given the beating the park’s roads take from harsh weather and tourist-season traffic, construction projects are typically under way during the summer in one corner or another of Yellowstone, so you may encounter significant delays while driving. Check out the park newspaper or website (nps.gov/yell) for the most current information on roadwork and detours.
August is the height of the tourist season in Yellowstone, which is one of the country’s most popular national parks. Campgrounds may be entirely full some nights, particularly over the weekend. Visitor centers and entrance stations display the status of each of the park's main developed campgrounds. Getting an early rise is usually the best bet for snagging a site in first-come, first-served campgrounds; Bridge Bay, Fishing Bridge, Canyon, Grant Village and Madison, meanwhile, take reservations (yellowstonenationalparklodges.com). While the park’s roads will be well-trafficked and its most popular attractions -- Old Faithful, for example, or the Hayden Valley -- thronged with people, you’re never far from solitude in a place as big and mostly roadless as Yellowstone. Strike out on virtually any hiking trail and you’ll leave the crowds behind; travelers in the deep backcountry may be fully alone.
All things considered, August is a fairly productive time to see wildlife in Yellowstone. The month usually coincides with the bison rut, when those enormous bovids are charged with breeding excitement. Particularly in the Hayden and Lamar valleys, you’ll have front-row seats to the drama. Park at a pull-out and use binoculars to watch the bulls testing cows and scrapping with one another, and the mingled herds occasionally erupting into dusty stampedes. Most of the elk herds are in the high country, but depending on prevailing weather conditions they may already be trekking into the lowlands ahead of winter. Grizzly and black bears will still be leading cubs around, and gray wolves are regularly traveling between rendezvous sites -- where the season’s growing pups hang out -- and hunting grounds.
Ranger programs -- excellent ways to deepen the whole family’s appreciation of Yellowstone -- are in full swing in August. They include guided interpretive hikes; informative talks on geology, ecology and history; and special astronomy and stargazing activities. Hikers usually find good conditions on Yellowstone’s extensive trail system in August, although on open-country routes you'll generally want to wrap up your hike by midday or spend the afternoon on a timbered route to avoid the intense sunlight and heat. Boaters, in turn, can take to massive Yellowstone Lake, bracingly cold throughout the summer, and bed down in far-flung campsites along the backcountry lakeshore.