13.3 miles
2,249 ft
-2,255 ft
2 miles
High Point

The top of Thunderbolt Mountain offers one of the most outstanding 360-degree views in the Helena area. All of the surrounding mountain ranges are visible from the peak. The high elevation and thick timber make this trail one of the last in the region to shed snow, and drifts are common into late June. The first part of the trail to Cottonwood Lake is very popular with backcountry horsemen and horsewomen, so be alert, and make sure to park courteously, leaving room for horse trailers to turn around.

The trail to Cottonwood Lake is a moderate climb. From the lake, the trail climbs steeply to the top of Thunderbolt Mountain. The junction is at the north end of the lake; if you carry on farther than that you have missed it and are headed into the Little Blackfoot watershed. Near the top, the trail skirts the CDT and recommended wilderness areas where bikes are not allowed, so resist doing any further exploring on your bike.

This ride also offers opportunities for connections with Little Blackfoot Meadows and Larabee Gulch to the north.

Take the Bernice exit of I-90 (Exit 151) and follow the Boulder River Road (staying to the left). Stay on the Boulder River road to the Thunderbolt Creek road, which is directly opposite the Whitehouse Campground. The junction is a distinctive Y and is signed. The Thunderbolt Creek road ends at the trailhead.

Local Trail Association
Montana Bicycle Guild (www.montanabicycleguild.org)
Please consider joining or donating to the local riding association to support trail development & maintenance.
donate to earn trail karma!


Post a Comment


  • Riding area
  • Primary Activity
    Mountain Bike
  • Difficulty rating
  • Route Type
    Out & Back
  • Bike type
    AM, XC
  • Direction
    One Direction
  • Physical rating
  • Ridelogs
More Stats for Thunderbolt Mountain mountain bike route
  • Altitude min
    6,382 ft
  • Altitude start
    6,388 ft
  • Altitude end
    6,388 ft
  • Grade
  • Grade max
  • Grade min
  • Distance climb
    6 miles
  • Distance down
    7 miles
  • Distance flat
    2,615 ft
Avg: 4 (1 votes)
Trail Conditions
  • Unknown
  • Snow Groomed
  • Snow Packed
  • Snow Covered
  • Freeze/thaw Cycle
  • Icy
  • Prevalent Mud
  • Wet
  • Variable
  • Ideal
  • Dry
  • Very Dry
Trail Ridden Direction
Trailforks scans users ridelogs to determine the most popular direction each trail is ridden. A good flowing trail network will have most trails flowing in a single direction according to their intension.
The colour categories are based on what percentage of riders are riding a trail in its intended direction.
  • > 96%
  • > 90%
  • > 80%
  • > 70%
  • > 50%
  • < 50%
Trail Last Ridden
Trailforks scans ridelogs to determine the last time a trail was ridden.
  • < 2 days
  • < 1 week
  • < 2 weeks
  • < 1 month
  • < 6 months
  • > 6 months
Trail Ridden Direction
The intended direction a trail should be ridden.
  • Downhill Only
  • Downhill Primary
  • Both Directions
  • Uphill Primary
  • Uphill Only
  • One Direction
Contribute Details
Colors indicate trail is missing specified detail.
  • Description
  • Photos
  • Description & Photos
  • Videos
Trail Popularity ?
Trailforks scans ridelogs to determine which trails are ridden the most in the last 9 months. Trails are compared with nearby trails in the same city region with a possible 25 colour shades. Think of this as a heatmap, more rides = more kinetic energy = warmer colors.
  • most popular
  • popular
  • less popular
  • not popular
Max Vehicle Width

Radar Time
Trail transparency

Recent Trail Reports Along Route

Thunderbolt Mountain Trail
Jun 13, 2021 @ 7:13pm
Jun 13, 2021
Cleared 30 or so trees and snow is gone until .4mi from thunderbolt mtn summit. Riding great!
L.O. Connection
Aug 24, 2020 @ 4:33pm
Aug 24, 2020
Thunderbolt Mountain Summit
Aug 24, 2020 @ 4:33pm
Aug 24, 2020
more reports »
  • flag
  • login to download gpx or kml files.