Winters are cold, with temperatures below freezing.
The frost-free season varies from 80 to 140 days, depending on altitude. Paper birch from the northern conifer forest is also present. Aspen covers considerable areas, presumably indicating fires in the past. Ponderosa pine dominates most lower slopes in the montane zone, with lodgepole pine from the Rockies found in small numbers. Along streams and rivers, eastern broadleaf species are common, including ash, hackberry, elm, birch, and bur oak.