In this breathtaking up-and-down country, temperature and climate vary as much as the terrain does, providing a rich seasonal variety of plants and animals. Precipitation may be in the form of snow any month of the year. Rain and the heavy upland winter snowfalls provide adequate moisture for the development of some of the nation's lushest natural grasslands, the sustenance, in turn, of large numbers of deer, elk, and other animals.
Historically, after staying close to the village in winter, the Nez Perce resumed their organized pattern of seasonal movement each spring, traveling to specific areas in a planned sequence. The areas to which they traveled were based primarily on the seasonal availability of plants, animals, and fish. The general pattern was to move higher in elevation as the season progressed, following the availability of maturing roots and berries. By late summer, most of the people were in the mountains, including the Bitterroot Mountains and the Big Hole valley. In the autumn they returned back to the river valleys of Idaho in time for the fall fish runs.
Severe winters are usual in this area. Winter temperatures frequently drop below 32 degrees F, and summer highs may reach only 70 degrees F. Precipitation varies from 20 to 40 inches per year and comes predominantly in snowfall during the winter months.