Hi Wayne, We've usually had one or two snowfalls in September, but not the big ones that indicate winter is here to stay. You can expect night time temperatures to be in the low 20's and day times up to high 60's and low 70's. (Cavaet: Of course, expect sudden winter weather conditions anytime in Sept/ October.) In addition to the Sawtooths, also keep in mind the Frank Church "River of No Return" Wilderness is relatively close to Boise. (Think McCall and head north out of Boise). The "Frank" is the largest Wilderness in the lower 48. Carol