4.8 miles
1,615 ft
-375 ft
Avg time


  • AKA
    Cottonwood Lake
  • Difficulty rating
  • Trail type
  • Bike type
    AM, XC, Fat
  • Trail Usage
  • Direction
    Both Directions
  • Climb Difficulty
    Black Diamond
  • Physical rating
  • Season
  • eBike Allowed
  • Global Ranking
  • Land Manager

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 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 via the L.O. Connection. 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.

Access Info

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
trail association logo
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!
More Stats for Thunderbolt Mountain Trail 65 mountain bike trail
  • Altitude change
    1,240 ft
  • Altitude min
    1.2 miles
  • Altitude max
    1.4 miles
  • Altitude start
    1.2 miles
  • Altitude end
    1.4 miles
  • Grade
  • Grade max
  • Grade min
  • Distance climb
    3.5 miles
  • Distance down
    1.1 miles
  • Distance flat
    1,520 ft
  • Avg time
  • view trail stats
on Aug 16, 2015
Avg: 4.5 (2 votes)

view (0)
Layers winter
Map Style
Trail Style
  • ?
update trails status or condition

Thunderbolt... Trail Reports

Aug 16, 2015 @ 11:17am
Aug 16, 2015
May 31, 2015 @ 6:57am
May 31, 2015
As of Memorial Day weekend, there were significant drifts in the last half-mile below Cottonwood Lake, and solid snow above the lake.
view all reports »

Technical Trail Features (TTF)


no photos have been added for Thunderbolt Mountain Trail 65 yet, add a photo.

Routes with this trail

Thunderbolt Mountain
13.3 miles

Reviews / Comments

No reviews yet, be the first to write a review or ask a question.
Use trail reports to comment on trail conditions.

Post a Comment

You must login to Pinkbike.
Don't have an account? Sign up

Join Pinkbike  Login


no videos have been added for Thunderbolt Mountain Trail 65 yet, add a video.

Nearby Trails

  • embed Thunderbolt Mountain Trail 65 trail on your website
    • Updated on Wed 2016-06-22 @ 12:06pm
    • Submitted on Fri 2015-06-05 @ 6:56am
    • By evasive MBG & contributors
    • #30743 - 471 views
  • subscribe
  • flag
  • login to download gpx or kml files.