“This is a short trail through fir forests to a great viewpoint overlooking Diablo Lake with views of snowy mountains.
— Joan Pendleton
Lake · River/Creek · Views
There is a small Thunder Knob parking area at Diablo Lake on the north side of the highway. From here, you'll need to run north through the campground to its far side to reach the Thunder Knob Trail.
The Thunder Knob Trail begins by almost immediately crossing Colonial Creek on a sturdy bridge. It then enters the fir forest and begins climbing gradually. The climb continues to the trail's end at the top of Thunder Knob. There are short sections of switchbacks in a few places on the climb, and occasional benches along the way to sit, rest, and enjoy the views.
As Thunder Knob Trail climbs, the views get better and better. One passes views of Diablo Lake and Thunder Creek Valley to the southeast, and Colonial Peak to the southwest, as the trail goes through thick fir forest. Eventually, the trees thin and get smaller as the trail nears the top of Thunder Knob, allowing more views in all directions.
From the top of Thunder Knob one can see turquoise Diablo Lake far below and snowy peaks in all directions. Diablo Lake is fed by Thunder Creek, with its glacier and snowmelt sources high in the mountains. More benches at the top of Thunder Knob give one a chance to linger, rest, and enjoy the views.