Diablo Lake lies deep in the in the North Cascades mountain range of northern Washington State, in the Ross Lake National Recreation Area and within North Cascades National Park in Whatcom County, Washington. Mountains surround Diablo Lake, without nearby cities and only a few tiny villages and towns. Diablo and Newhalem, Washington, are on the western edge of Diablo Lake at the base of Sourdough Mountain. These towns are unincorporated company settlements established by Seattle City Light, home of the Skagit Hydroelectric Project on Diablo, Gorge, and Ross Lakes in the North Cascades.

Diablo Lake covers 803 acres at an elevation of 1213 feet with a maximum depth of 320 feet. The Skagit River feeds Diablo Lake. The Seattle City Light power company manages Diablo Lake. Diablo Lake is 125 miles northwest of Seattle, Washington. Diablo Lake’s the water temperature rarely exceeds 50° F, even in summer. Fine glacier sediment, called glacial flour, gives its waters a brilliant turquoise luminosity. Thunder Creek, which drains over fifty glaciers into Diablo Lake, creates this beautiful phenomenon.

Washington State Route/SR 20 also known as the North Cascades Highway follows Diablo Lake’s southern shores and stretches from Anacortes, Washington, on the west coast to Okanogan, Washington, on the east. Diablo Lake is open year round. The winter season causes the regular closure of SR 20, depending on snow and avalanche conditions.

Diablo Lake’s water is the most vivid color on sunny days in July, August, and September when seasonal glacial melt occurs. Few people visit the North Cascades from October in the upper elevations to until mid-to late April.

History of Diablo Lake

The Cordilleran Ice Sheet developed over British Columbia, Washington State, and the surrounding areas repeatedly during the Pleistocene era. Around 9,000 years ago, as the Cordilleran Ice Sheet retreated, the Native American tribes of Upper Skagit, Swinomish, Sauk-Suiattle, and Nlakapamuk began to explore the Diablo Lake region in the Upper Skagit Valley and surrounding mountains. Archeologists have found hunting, gathering, salmon drying processes, and quarrying evidence in over 160 pre-European contact archeological sites recorded in the upper Skagit Valley.

In 1902, the City of Seattle issued a $590,000 bond for hydroelectric power on the Skagit River. This marked the beginning of public power in Seattle, and it was the nation's first municipally owned hydroelectric project. In 1995, Seattle City Light negotiated a new licensing agreement with groups of state, federal, tribal, and environmental entities to help improve fisheries, wildlife, recreation, cultural resources, and the visual environment near the Diablo, Gorge, and Ross Dams.

Newhalem is the original company village for Seattle City Light employees. Newhalem is 11 miles downstream on the Skagit River from Diablo Lake. It derived its name from a Native American word meaning “goat snare”. About 10,000 years ago, indigenous Northwest peoples began to visit the upper Skagit Valley and the surrounding mountains. They adapted to the new landscape, which the melting of massive glaciers stretching across British Columbia and northern Washington revealed.

The Skagit Valley became home to several Native American tribes known as the Coastal Samish, which comprised two linguistic groups: the Straits, including the Clallam, Lummi, Samish and Semiahmoo tribes and the Lushootseed, including the Skagit, Snohomish, Snoqualmie, Swinomish, and Upper Skagit. Goats were important for meat and the extremely warm wool products, which they frequently traded with other indigenous groups for goods.

Ancient rock quarries are scattered throughout the upper Skagit Valley, where the ancestors of today’s Indians gathered, cleaned, and shaped Hozomeen chert, which is similar to flint, to make knives and other tools. The oldest of these quarries has been radiocarbon dated to 8,400 years old. They also traded with tribes for obsidian from eastern regions to use in making other tools.

The Samish accessed a wide variety of traditional foods. Women and children gathered sprouts, bulbs, roots and shoots, berries, shellfish, sea urchins, and crab. Men used beach seines, reef nets, and weirs to manage fish runs, which included all five species of Pacific salmon, smelt, herring, steelhead trout, halibut, sucker, chub, and occasionally sturgeon. They also formed hunting parties for upland birds, waterfowl, small game, deer, elk, and seal in season.

The first written record of the upper Skagit Valley is from Henry Custer’s 1859 boundary survey explorations. Fraser River Indians served as their guides for this expedition, and they traveled in a dugout canoe specially built for their trip near today’s Hozomeen. Today, Skagit River tribal governments comprising the Upper Skagit, Sauk-Suiattle, Swinomish, Nlakapamux, and the First Nation of British Columbia tribes provide insight and advice regarding archeological sites and other resources relating to their traditional connection to the North Cascades.

J.D. Ross was Seattle City Light’s second superintendent with a vision that has stood the test of time. He won approval to build hydroelectric power plants on the Skagit River. Newhalem is one of the last company towns surviving in the U.S. Ross is responsible for building the dams on Gorge, Diablo, and Ross Lakes. He established Newhalem and built a beautiful garden at Newhalem’s Gorge Powerhouse, the Ladder Creek Falls Garden.

Ross built a trail to along Ladder Creek Falls to showcase the area. The garden features a light show that runs from dusk to midnight daily. Signs mark the informative paved trail near the powerhouse, and there are benches for resting while strolling through ferns, mosses, flowers, shrubs, and trees, many of which are not indigenous, like tea, lemon, and grapefruit. The illuminated path leads upward 400 feet past lily ponds.

Ross imported tropical plants for the garden and monkeys for Monkey Island and deer for Deer Island in Diablo Lake. It was too cold for the monkeys at night, so they  brought  the monkeys inside. The deer could swim and escaped their island. The Skagit Project enjoyed a national reputation, promoted hydroelectricity, and municipal ownership before World War II. Thousands of tourists visited Diablo Lake to take part in two-day tours of the Project by rail and boat in the early 20^th century.

Fishing Diablo Lake

Naturally reproducing rainbow trout are the main game species in Diablo Lake. Other species are cutthroat trout, eastern trout, and bull trout. Fishing licenses are not sold at any visitor or information station in the North Cascades National Park, and you must obtain a license before fishing. Diablo Lake is open year round, but is not always accessible by vehicle in winter months.

Washington has protections in place for bull trout, a type of char in the trout family that has declined in numbers in most Western waters over the years. It is not legal to take bull trout from Diablo Lake, so if you catch one, release it quickly and unharmed. Motorized boating is allowed with restrictions. Four-stroke motors, direct-injection two-stroke engines, or equivalent technology are required. Towing is strictly regulated on Diablo Lake.

Fishing is permitted from public boat docks unless posted signs prohibit this activity. The trout are not as active in April and October, but anglers do find them. July and August are too hot. May, June, and September are the best trout fishing months. Trolling for trout is a great option Diablo Lake, but you may need to cover more water to find the fish.

Anglers are required to get a backcountry permit year round for overnight boating, hiking, or skiing. Handwritten self-issue permits are available outside at the Wilderness Office at Marblemount, 23 miles south of Diablo Lake on SR 20. You can register for winter permits by email in winter at [email protected]. The email is checked intermittently during the winter.

Diablo Lake has three boat-in campgrounds, Thunder Point with three campsites, Hidden Cove with its single site, and Buster Brown with three sites. Canoes and kayaks must be portaged between Diablo and Ross Lakes on the Skagit River. Boaters on Diablo Lake must use the portage dock for canoes and kayaks and are not allowed to use the ferry dock. The portage is 1.2 miles over a gravel road, with an elevation gain of 525 feet. Motorboats can launch at Colonial Creek Campground, and there are no marinas on Diablo Lake.

North Cascades National Park Service Complex Prohibits:

• Fishing in fresh waters in any manner other than by hook and line, with the rod or line being closely attended.
• Two pole fishing on Diablo Lake.
• Possessing or using as bait for fishing in freshwaters, live or dead minnows or other bait fish, amphibians, non-preserved fish eggs or fish roe, except in designated waters.
• Chumming or placing preserved or fresh fish eggs, fish roe, food, fish parts, chemicals, or other foreign substances in fresh waters for the purpose of feeding or attracting fish in order that they may be taken.
• Commercial fishing, except where specifically authorized by Federal statutory law.
• Fishing by the use of drugs, poisons, explosives, or electricity.
• Digging for bait, except in privately owned lands.
• Failing to return carefully and immediately to the water from which it was taken a fish that does not meet size or species restrictions or that the person chooses not to keep. Fish so released shall not be included in the catch or possession limit, provided, that at the time of catching the person did not possess the legal limit of fish.
• Fishing from motor road bridges, from or within 200 feet of a public raft or float designated for water sports, or within the limits of locations designated as swimming beaches, surfing areas, or public boat docks, except in designated areas.
• Introducing wildlife, fish, or plants, including their reproductive bodies, into a park area ecosystem. This includes the discarding and/or dumping of bait and bait buckets.
• The use or possession of fish, wildlife, or plants for ceremonial or religious purposes, except where specifically authorized by Federal statutory law, or treaty rights.

Boating Diablo Lake

Kayaking, canoeing, and motor boating are popular activities on Diablo Lake. There are no boat rental options at Diablo Lake. Canoes and Kayaks can be portaged between Diablo and Ross Lakes on the Skagit River, and also in Colonial Creek Campground which has the motorboat launch. No waterskiing or tubing is allowed on Diablo Lake. Towing is strictly regulated on Diablo Lake.

There are no marinas on Diablo Lake. There is no direct road access from the south, but canoes, kayaks, other portable watercraft, and motorboats. Boaters on Diablo Lake cannot use the ferry dock. Motorized boating is allowed with restrictions. Four-stroke motors, direct-injection two-stroke engines, or equivalent technology are required.

With lofty snow-capped mountains on either side of Diablo Lake, vibrant turquoise water, the Diablo Dam, and several islands to visit in a boat, boaters take in breathtaking scenery and nature. Diablo Lake can become dangerously windy, so keep your eye on the weather.

Plan your next outing on our Diablo Lake Boat Ramps Map, and keep an eye on the Diablo Lake Level. Find or sell a boat on our Diablo Lake Boats for Sale page.

Diablo Lake Cabin Rentals

There are No Diablo Lake Cabin Rentals and Vacation Homes

Diablo Lake is located within the North Cascades National Park, and there is no private property ownership, and none of the campgrounds have cabins. 

Camping at Diablo Lake

There are 94 campsites with RV sites and ten walk-in, tent-only sites at Colonial Creek Campground on the southern arm of Diablo Lake. There are several options for the drive-in campsites, but you must book reservations quickly and in advance. If you don’t have a reservation, try to arrive by midmorning. Amenities include:

• Amphitheater
• Boat Ramp
• Boat Trailer Parking
• Fishing Pier
• Host
• Lake Access
• Parking Area
• Paved Parking
• Paved Roads
• Pets Allowed
• Picnic Tables
• Recycling
• Trash Collection
• Water (Seasonal)
• Campfire Rings
• Food Storage Locker
• Tent Pads

The Buster Brown, Hidden Cove, and Thunder Point campgrounds are primitive boat-in campgrounds. Buster Brown and Thunder Point have three campsites, and Hidden Cove has one. They have toilets, but you must bring everything you need with you. Campfires and pets are allowed.

Check out our list of campgrounds and RV parks for your family adventure on our Diablo Lake Camping page.

Trails at Diablo Lake

Hikers need a backcountry permit year round for overnight hiking. Handwritten self-issue permits are available outside at the Wilderness Office at Marblemount, 23 miles south of Diablo Lake on SR 20. You can register for winter permits by email in winter at [email protected]. The email is checked intermittently during the winter.

The Diablo Lake Trail is on the north side of Diablo Lake and 7.6 miles with an elevation gain of 1,400 feet, with the highest point at 1,950 feet. From the trailhead, it is 3.5 miles to the lake. Drive east on SR 20 and across the Gorge Lake Bridge. Continue for 1.5 miles and turn left onto Diablo Dam Road. From there, follow signs for the North Cascades Environmental Center to get to the Diablo Trail trailhead.

The Thunder Creek Trail is 12 miles round trip with an elevation gain of 1,300 feet and the highest point at 1,900 feet. Campfires are allowed only at designated lower elevation camps. Pets are not allowed. Thunder Creek carries a heavy load of glacial flour. Early 19^th century prospectors and trappers opened this trail. Mining developers and the US Forest Service made major improvements in the early 1900s. There are several hiking camps along the trail.

To get to the Thunder Creek trailhead, follow State Route 20 to mile 130, Diablo Lake. Enter the south side of Colonial Creek Campground and park in the large lot above the boat ramp. Horses should access this trail via the trailhead that lies uphill from the parking lot behind the trailer dump station. This is the preferred trailhead for horses. Hikers and backpackers should walk the length of the campground, following the signs to the amphitheater, where the main trail begins.

The Thunder Knob Trail is 3.6 miles round trip with an elevation gain of 635 feet and the highest point at 1,875 feet. It is well marked and a suitable hike for children. The bridges over the streams on this trail are taken down in the winter to keep them from damage. Colonial Creek on this trail can be temperamental and can change directions and flood everything in its path. Dogs on leashes are allowed. There are seasonal road closures. The trailhead begins at Colonial Creek Campground.

The Sourdough Mountain Trail is 10.4 miles round trip with an elevation gain of 4,870 feet and the highest point at 5,985 feet. Sourdough Mountain was one of the first lookouts established by the U.S. Forest Service. Beatnik poets Gary Snyder and Philip Whalen, who worked as lookouts during the 1950s, found Sourdough Mountain to be their poetic inspiration.

This trail climbs up out of towering conifers into open meadowlands with breathtaking views. In the first two miles, hikers face a climb of 3,000 vertical feet with rough switchbacks. Then, the forest gradually thins and at four miles in, you need to cross Sourdough Creek carefully, and the grade becomes less steep. From Marblemount, drive SR 20 east for 20 miles. Turn left on Diablo Road and proceed 0.7 mile. Cross the Stetattle Creek Bridge, bear right and reach the trailhead in 0.25 mile.

Things to Do At Diablo Lake

The Environmental Learning Center is an award-winning educational campus built on the northern shores of Diablo Lake. The Skagit River Hydroelectric Project built the center and manages it in partnership with the North Cascades Institute, the National Park Service, and Seattle City Light. Activities based at the Learning Center include school and youth programs and classes for adults, teachers, and families, plus it offers overnight packages and tours with a ranger. The Family Stays package includes guided hikes, canoe trips, outdoor games, arts and crafts, fireside storytelling, and night-time walks. The Base Camp package for adults offers guided tours and naturalist talks. 

The free Newhalem Walking Tour is a great way to visit the historical company town. You can learn about the area’s hydroelectric history, kilowatts, turbines, spill gates, and how many households and businesses the project can power. The area is rich in cultural stories in an amazing alpine area.

Formerly known as the “Fishermen’s Ferry”, Seattle City Light offers a ferry service/tour across Diablo Lake twice daily from June through October. The ferry travels between the West Ferry Landing near Diablo Dam to the East Ferry Landing on upper Diablo Lake near Ross Dam. The ferry transports guests staying at the Ross Lake Resort and provides access to Ross Lake for hikers and campers heading to the backcountry areas.

Diablo Dam is on the upper Skagit River in Whatcom County, Washington, and part of the Skagit River Hydroelectric Project that supplies Seattle with some of its power needs. The dam was built in Diablo Canyon, a gorge of solid granite with vertical walls That rise 160 feet above the riverbed. Visitors love to drive across the dam for splendid views of Diablo Lake and the Skagit River.

Drive up SR 20 to the Diablo Lake Vista Point for an amazing photo opportunity. The Diablo Lake Overlook is 11 miles east of Newhalem on SR 20, with gorgeous views over Diablo Lake to Diamond Peak. The complete length of SR 20 is a popular epic road trip.

Stay overnight in the nearby tiny township of Marblemount at the Buffalo Run Inn, only 30 minutes west of Diablo Lake. Its historic 1889 old growth cedar roadhouse was a frequent watering hole for gold miners, mountain men, lumberjacks, and mule trains traveling up the Skagit River into the North Cascades mountains. Today, it is a luxurious bed-and-breakfast with the famous Buffalo Run Restaurant across the street.

Take an air tour of the Cascades Mountains with Snowking Aviation. They offer four different air tour packages for scenic photography flights, an air ferry service, and flight training. They operate from March to October. Groups are limited to three passengers or a total weight of 450 lbs. For larger groups, they will arrange multiple flights. Snowking Aviation is located at 7879 South Superior Avenue, Mears Field, Concrete, Washington, and only eight miles from Diablo Lake Overlook.

Plan your next adventure on our What To Do At Diablo Lake page, and the Diablo Lake Event Calendar.

Diablo Lake Weather & Climate

Diablo Lake sees an average of 42 inches of rain, with five feet of snow, and 158 days of sunshine per year. The winter low in January is 34 degrees, with a summer high in July of 73 degrees. July, August, and September are the most comfortable months for this region, while December and January are the least comfortable months.

Keep an eye on the skies with our Diablo Lake Weather Forecast page.

Diablo Lake Zip Codes

Whatcom County: 98220, 98225, 98226, 98227, 98228, 98229, 98230, 98231, 98237, 98240, 98244, 98247, 98248, 98262, 98264, 98266, 98276, 98281, 98283, 98295.

Diablo Lake Flora and Fauna

Elusive mammals like the grizzly bear, gray wolf, fisher, and wolverine wander the wilderness in small numbers, while more adaptable Columbia black-tailed deer, Douglas squirrels, and pikas are more common. A wide variety of birds breed within the Northern Cascades, including rare birds like bald eagles, ospreys, and Harlequin ducks, plus a variety of neotropical migrant birds. The North Cascades is home to approximately 75 mammal species in 20 families, around 21 species of reptiles and amphibians representing at least four orders, and about 200 species of birds in 38 families.

Plant life in the North Cascades varies greatly and reflects differences in rock and soil types, exposure, slope, elevation, and rainfall. Eight distinctive life zones support thousands of different plant species in the North Cascades’ greater ecosystem. No other US National Park surpasses North Cascades National Park in the number of plant species recorded.

Conifers, the cone-bearing trees, dominate the forests of the North Cascades. They span the elevation ranges from sea level to the alpine zone, shelter the low valleys, and cling to the thin mineral soils of the high peaks. Species of maple, poplar, and alder grow in the natural openings and broad-leaved trees grow along the edges of streams and rivers where there is more sunlight.

Wildflowers are everywhere in the North Cascades. They occur across the entire range of habitat types from wet hillside seeps and moist, shady forest floors to dry east-side slopes and exposed alpine ridges. They are simple and ornate, and grow alone among ancient hemlocks, or as magnificent displays in open alpine meadows. The significant differences in elevation, exposure, and precipitation that exist in the North Cascades promote a range of flowering times. Some plants are flowering by late February and early March in the low elevation forests, and others as late as August and early September in the alpine zone.