Some areas in Montana and Wyoming are at an elevation of 2,100 to 3,000 m, and mountain peaks are almost 4,300 m. High mountains having steep slopes and sharp crests are cut by narrow valleys, most of which have steep gradients. Lakes are common, especially in glaciated areas. Average annual precipitation Mainly 625 to 1,525 mm, increasing with elevation, but almost 375 mm in the western part of the area and almost 2,550 mm in high mountains. Most of the precipitation during fall, winter, and spring is snow.
Summers are dry.
Average annual temperature 2 to 7 C in most of the area, but it is 8 C or more at low elevations. Average freeze-free period 45 to 120 days, decreasing with elevation, and as long as 140 days in low valleys of Washington. Moderate precipitation and many perennial streams and lakes provide ample water. Streams and reservoirs supply water to adjoining MLRA's for irrigation and other uses. Springs and shallow wells in the valleys provide water for domestic use and for livestock.