Thunder Knob is a 3.8-mile round trip to a Diablo Lake view, and fall is when the trail earns its keep
Most people see Diablo Lake from a roadside pullout, snap a photo, and keep driving. That’s a perfectly good plan, but it skips the better one. A short trail right off Highway 20 puts you on a knob high above the water, with benches to sit on and nobody rushing you back to the car.
Thunder Knob is not a big, bragging-rights hike. It’s the kind of trail you can do after a late start, with kids or with a friend who swears they “don’t really hike.” Fall might be the best time to try it.
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What the hike actually asks of you
According to the National Park Service, the trail runs 1.9 miles one way, so about 3.8 miles round trip, with roughly 680 feet of elevation gain. The grade is moderate and the path is well built, which is why it’s rated easy to moderate and suits families.
The trailhead sits on the north side of Highway 20 at milepost 130, at the entrance to Colonial Creek Campground. It’s about 24 miles east of Marblemount and 63 miles west of Winthrop, and it’s signed, so you won’t be hunting for it.
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Why fall suits this trail
The park service points out flame-orange vine maple color here in autumn, and that’s the part that makes this a fall trail. The forest sections of the hike are shaded Douglas fir, redcedar and western hemlock, so the maples pop against all that dark green.
The start is rockier than you’d expect. You cross an old creek bed with uneven footing, so watch your steps and follow the rock cairns until the path settles into the trees.
The payoff at the top
Around the one-mile mark, the trees open into a sunny, dry clearing with a bench and a view of Colonial Peak. It’s a natural place to catch your breath, and honestly, the bench alone is a good reason to bring a thermos.
The last stretch passes a small pond and climbs gently to a knoll with several viewpoints. Benches look out over Diablo Lake, with Davis Peak rising to the west, Colonial and Pyramid peaks to the south, and Jack Mountain to the northeast.
That famous turquoise color comes from glacial rock flour suspended in the water, and it’s strongest in summer. In fall the lake can look a little moodier, which, in my opinion, makes for a better photo with the changing leaves.
Before you go
Dogs are allowed on a leash, and the trail is for hikers only. There’s no backcountry camping, but you can car camp at the trailhead campground if you want to turn this into a weekend.
Highway 20 closes for winter, and conditions can change quickly in the mountains, so check the Washington State Department of Transportation road status before you drive out. Want to see more of the park? Our guide to the best hikes in North Cascades National Park has plenty of ideas for the next trip.
Trip tips: grab a rental car to get out here, lock in your hotel before the good rooms are gone, or skip both and book a camper van instead.
Have you hiked to Thunder Knob, or do you still stop at the overlook and keep driving? Tell us in the comments.
