The Boulder Mountains are a mountain range running roughly north to south located west of Boulder between Helena and Butte in the U.S. state of Montana. Parts of the range are in four different counties: Deer Lodge, Jefferson, Lewis and Clark, and Silver Bow. Haystack Mountain, which reaches 8819 ft, is the tallest peak in the range. The three other highest peaks are Jack Mountain at 8752 ft, Bull Mountain at 8609 ft, and Thunderbolt Mountain at 8597 ft. All four peaks are in Jefferson County.

Climate

Rocker Peak, 8455 ft, is near Jack Mountain (Montana), the second highest peak in the Boulder Mountains. There is a SNOTEL weather station near the summit of Rocker Peak at an elevation of 8000. ft. Rocker Peak has a subalpine climate (Köppen Dfc), bordering on an Alpine climate (Köppen ET).