5 - 6
FATMAP difficulty grade
The Thornton Lakes are suspended in a high-alpine valley below jagged, rocky mountain peaks.
These crystal-clear lakes are a popular backpacking destination in North Cascades National Park, with beautiful campsites available near the shore of the lower lake. The 9-mile round-trip route might not sound too long, but with about 3,500 vertical feet of elevation gain, it makes for a stiff but achievable day hike. The hike to the lake starts off easy, following "a brushy old road grade for the first half of the trail with minimal elevation gain," according to [PlanetWare.com](https://www.planetware.com/washington/top-rated-hikes-in-north-cascades-national-park-us-wa-130.htm).
Then, the route reaches a true trail and a real climb as it quickly begins ascending steeply up to a ridgeline, finishing with a series of steep switchbacks.
On the ridge, you'll enjoy stunning views of the North Cascades, including Teebone Ridge, Skagit Valley, and Trapper Peak.
If you take a right on top of the ridge, you can continue climbing to the summit of Trapper Peak. Once you're done admiring the view, you'll drop down a steep half-mile to the lakes, where you'll find the campsites along the lakeshore.
Note that a permit is required for overnight camping, but not for day hiking. Sources: https://www.planetware.com/washington/top-rated-hikes-in-north-cascades-national-park-us-wa-130.htm https://www.earthtrekkers.com/best-hikes-in-north-cascades-national-park/