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Thunder Knob

North Cascades


North Cascades -- North Cascades Highway - Hwy 20
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3.6 miles, roundtrip


Gain: 635 ft.
Highest Point: 1875 ft.


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WTA worked here: 2013

Parking Pass/Entry Fee

A backcountry permit is required to camp overnight in North Cascades National Park. Permits must be picked up in person at one of the park's Wilderness Information Centers

Hike this easy leg stretcher while taking in the beautiful scenery of the North Cascades Highway. A good stop if you have a car full of restless children or you are showing off the area to visiting relatives. The views from the top are a big payoff for such a short hike.

Begin your hike by walking through the campground along the well signed trail for Thunder Knob. Reach a braided Colonial Creek and cross on a series of bridges. This creek has been known to be a bit temperamental, changing directions and flooding everything in its path. If you are hiking this in the winter, be aware that the bridges are taken down at the end of the summer season to prevent the river damaging them.

Once across the river, you will see the former rocky creek bed. Follow the rock-lined path through it, and end up at the edge of the forest. Enter the forest and notice how beautifully green it is, a mossy carpet under the hemlock and salal and draped over decaying logs. As you work your way up a bit higher, watch how the forest changes in just a matter of a few hundred feet. Now it is a drier forest of lodgepole pine, the ground is more rocky and exposed, the moss gone. The forest you just hiked through is just low enough to catch moisture, while the higher trail shows the effect of a small rain shadow created by the surrounding peaks.

Rest on one of the benches, or take a few pictures of Colonial Peak at this first viewpoint. After the viewpoint, the trail climbs a little, then heads down and across a marsh. The marsh can be quite scenic when full of water, reflecting the grasses at the edge, but may dry up later in the season.

From the marsh, hike up and reach the top of Thunder Knob. A short spur to the left will take you to benches to rest, eat a snack (but watch out for thieving chipmunks), and take in the views. From this viewpoint, look below you at the clear turquoise water of Diablo Lake (actually a reservoir) and Diablo Dam in the distance. Diablo Dam was completed in 1930 and at 389 feet was the highest dam in the world at that time.

The beautiful opaque turquoise water is a result of 'rock flour', silt that is carried downstream from underneath melting glaciers high in the peaks above. The tiny particles are suspended in the water and the way the light is reflected off the lake is perceived by our eyes as the striking blue green. If you hike earlier in the year, the color will be bluer, in late summer, the color will be greener.

Look up and see the ridge of Sourdough Mountain and the snowfield of Davis Peak. A short trail leads to another viewpoint, looking across toward Jack Mountain and down toward the narrow channel of Diablo Lake. The valley still looks steep and wild; imagine for a minute what the Skagit River and this valley once looked like before the dams were built. Return along the same path.

WTA Pro Tip: There is so much to see and do in the North Cascades. Stay at Colonial Creek campground and hike more of the many trails close by. The Pyramid Lake trail is a fairly short trail signed just after you cross Gorge Lake. The Thunder Creek trail is long but gentle as it follows Thunder Creek up a wild valley. It takes off at the end of the campground on the other side of highway 20.

On your way back, stop and hike to Ladder Falls, a short hike behind the power plant in Newhalem. At night, this path has a colored light show.


Thunder Knob

Map & Directions

Co-ordinates: 48.6905, -121.0980 Open map in new window


North Cascades -- North Cascades Highway - Hwy 20

North Cascades National Park

See weather forecast

Guidebooks & Maps

Day Hiking: North Cascades (Romano - Mountaineers Books)

Buy the Green Trails Diablo Dam No. 48 map

Getting There

Take Highway 20 east past Newhalem. Cross Gorge Lake, and follow the shoreline of Diablo Lake until you reach Colonial Creek campground, past milepost 130. Turn left and park at the trailhead to the right of the campground entrance.

The trail starts here, not in the campground. There is a pit toilet somewhat hidden behind a tree, and flush toilets along the campground entrance road, open when the campground is. This trail has been listed as wheelchair accessible, but that is no longer the case.

Parking Pass/Entry Fee

A backcountry permit is required to camp overnight in North Cascades National Park. Permits must be picked up in person at one of the park's Wilderness Information Centers

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Thunder Knob

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