5 miles
1,543 ft
-300 ft
Avg time
Trail Supporters, Builders & Maintainers of Thunderbolt Mountain 65 Trail


  • Riding Area
    Helena, Montana
  • 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
More Stats for Thunderbolt Mountain Trail 65 bike trail
  • Altitude change
    1,243 ft
  • Altitude min
    6,393 ft
  • Altitude max
    7,636 ft
  • Altitude start
    6,393 ft
  • Altitude end
    7,636 ft
  • Grade
  • Grade max
  • Grade min
  • Distance climb
    4 miles
  • Distance down
    5,057 ft
  • Distance flat
    1,179 ft
  • Avg time
  • view trail stats
on Nov 1, 2017
Snow Covered
Avg: 4.5 (2 votes)

view (0)
Layers winter
Trail Style
  • ?
Activity Type
Trail Conditions
  • Unknown
  • Snow Packed
  • Snow Covered
  • Freeze/thaw Cycle
  • Icy
  • Prevalent Mud
  • Wet
  • Variable
  • Dry
  • Very Dry
Directions to thunderbolt-mountain-trail-65 trailhead (46.283170, -112.473850)
update trails status or condition

Thunderbolt... Trail Reports

Nov 1, 2017 @ 11:24am
Nov 1, 2017
reporter First real snowfall of 2017/18
Sep 18, 2017 @ 1:00pm
Sep 18, 2017
Sep 16, 2017 @ 11:37am
Sep 16, 2017
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 »


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Routes with this trail

Thunderbolt Mountain
13 miles

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