Thornton Lakes Trail

Dogs No Dogs

Features Birding · Commonly Backpacked · Lake · River/Creek · Swimming · Views · Wildflowers · Wildlife

The Thornton Lakes Trail is a nice day trip or overnight to a subalpine lake with views of the rugged North Cascades Peaks. The first two miles of trail gently ascend an old road grade through new growth forest. Then, the trail trail climbs steadily upwards through mature hemlock forest until it reaches meadows and attains the ridge. The ridge offers spectacular views of Triumph Peak and lower Thornton Lake.

The short, steep trail down to lower Thornton Lake is often muddy and slippery. Be especially careful on the rock and floating-log scramble to cross the outlet of the lake and reach the camp.

A backcountry permit is required for all overnight stays in the national park. Camping in the Thornton Lakes area must be at one of the three designated sites. Permits are limited an fill up quickly, so make sure to check on Recreation.gov or with a ranger station for availability.

The trail starts at Thornton Lakes Trailhead and follows an old road grade for 2.3 miles through new-growth forest. This area was logged in the 1960's before the park was established. The trail is surrounded by a natural mix of Douglas-fir, Pacific silver fir, hemlock, cedar, alder, maples, and various shrubs that can prove bothersome.

At the third switchback, the trail steepens and continues to climb up many moderate to steep switchbacks. The trail ascends through forested slopes, through a wet meadow and over a creek before officially entering North Cascades National Park. At 4.5 miles, the trees thin, and the trail breaks out into meadows of heather and huckleberry, continuing to climb to an open ridge. From the ridge, you get expansive views of Mt. Triumph, Teebone Ridge, and the Skagit Valley.

A scramble route leaves the main trail at the ridge and ascends steeply towards Trappers Peak. If you spend the night at Thornton Lakes, this can be a great extension of your trip. The views from Trappers Peak of the three Thornton Lakes and the rugged Picket Range are truly spectacular.

The main trail descends steeply for 0.6 miles down 500 ft along a lesser ridge with views of lower Thornton Lake and Triumph Peak beyond. This trail is steep and is often muddy and slippery. Be especially careful where the trail crosses the lake outlet on rocks and logs. This crossing is necessary to reach the camp, which has 3 backcountry sites and a compostable toilet.

From lower Thornton Lake there is a primitive climber's path that proceeds to the upper lakes and Triumph Col. The two lakes above are cupped in their own rocky basin, forming classic cirque lakes that were created by glaciers which carved the rock basin before retreating to where they are today. A scramble up this primitive trail makes a worthy side trip if you are camping at the lower lake.

This ecosystem has very fragile vegetation. Make sure to avoid trampling vegetation by running and resting only on durable surfaces such as the trail, snow, or rocks. Wildlife in this area include deer, bear, marmot, and birds. Hawks and eagles can be observed during autumn migration.