Diablo Lake in Seattle 2025

Turquoise lake in North Cascades surrounded by peaks and lush forests

Best time: May–September

Situated in the North Cascade mountains of Washington state, Diablo Lake lays between Ross Lake and Gorge Lake on the Skagit River at the height of 1,201 feet (366 m). The lake is part of Ross Lake National Recreation Area and is a popular camping, hiking, kayaking, and fishing destination. Rainbow, coastal cutthroat, brook, and other trout species live in this lake. The lake is famous for its turquoise water color as well. The water stays freezing even during the summer due to glacial waters. Diablo Lake's best season for hiking and water sports runs from May through September (late May to early September for camping).

Camping on Diablo Lake is possible with a permit. There are three boat-in camping sites on Diablo Lake. There is also a Colonial Creek Campground on State Route 20.

Diablo Lake Trail is a 7.5 miles long, starting at the North Cascades Institute parking lot. It begins not far from Marblemount, Washington, and features mild elevation gain of 1500 ft (457 m). The trail goes through rocky fields, rain forest-like areas, and dry open plains. Hikers pass talus slopes of Sourdough Mountain, waterfalls, and enjoy beautiful views of Pyramid, Ross Lake, Snowfield, Davis Peaks, and Jack Mountain.

The trail goes straight to the suspension bridge at Ross Dam, but the path down to the bridge is rather steep, so if you are hiking with dogs and children, it might be better to stay by Diablo Lake and enjoy its beautiful vistas.

Practical info

When would be the ideal time to visit Seattle's Diablo Lake?

Seattle's Diablo Lake should be visited from May through September, as this is the best season with warm weather, ideal for outdoor activities like fishing, boating, and hiking. The lake also experiences a peak camping season between late May and early September. Due to the lake's glacial source, the water can become freezing even during summertime.

Where can one find Diablo Lake in Washington State?

Diablo Lake is a part of the Ross Lake National Recreation Area and is situated in the North Cascade Mountains of Washington, nestled between Ross Lake and Gorge Lake. It is conveniently reachable through State Route 20 and a short distance away from Marblemount, Washington. The surroundings of the lake are made beautiful by snow-clad peaks, vast meadows, and dense forests for visitors to explore during camping and hiking trips.

What are the available camping options for visitors to Diablo Lake?

Diablo Lake provides three boat-in camping sites for permit holders. Meanwhile, the Colonial Creek Campground is easily accessible through State Route 20 and provides traditional camping amenities. The primary campsites include restrooms with running water, showers, picnic tables, and other facilities for use. Hiking is also an accessible camping option, with several campsites accessible along the way. Visitors can find whatever they need at Diablo Lake for their vacation, with the campsites being a great starting point for explorers enjoying water sports and hiking.

What kind of fish can one fish in Diablo Lake?

Diablo Lake is an ideal fishing destination, with its frigid glacial water sustaining several fish species throughout the year. Lovers of angling can try fishing for rainbow, coastal cutthroat, and brook trout. Catfish, black crappie, bass, Northern pike, and pumpkinseed sunfish, are also popular among fishing enthusiasts. Fishing is permitted year-round, with fly-fishing also a viable option in upper Skagit River. This fishing haven is a must-visit for fishing enthusiasts.

What sights can hikers experience during their treks in the Diablo Lake Trail?

The Diablo Lake Trail attracts hikers to its picture-perfect, 7.5-mile long stretch, which commences from the North Cascades Institute parking lot. Hikers can explore the trail's diverse landscapes, from rocky fields to rainforest-like areas and open plains. Moreover, hikers can take in the stunning vistas of the Pyramid, Ross Lake, Snowfield, Davis Peaks, and Jack Mountain, and even come across various wildlife and waterfalls. The trail concludes at Ross Dam's suspension bridge, which offers fantastic views of the surrounding mountain ranges and the lake, making it a satisfying hiking experience for nature lovers.