City of Rocks is located in south-central Idaho within the northern edge of the Basin and Range geologic province. Outdoor recreation can be pleasant from April through October with June and September offering the most ideal weather. Summers are generally dry with temperatures ranging from lows in the upper 40's to highs in the upper 80's, but prepare for extremes. On rare summer nights in the upper elevations above 6,000 feet, temperatures have dipped into the 30's; and on rare occasion, the Almo Valley below 5,500 feet has experienced midday highs reaching 100° F. Afternoon thunderstorms are common in the summer months (June - August)
Average winter weather includes lows in the upper teens and daytime highs in the low 40's. Snow can accumulate up to 12-16 inches at times in the Almo Valley and over 24 inches in the Reserve, but typically the valley snow melts to within a few inches, but can drift to four feet in the higher elevations of the Reserve.