Blanca Lake, Mountain lake in Snohomish County, Washington, United States

Blanca Lake lies in a basin in the Henry M. Jackson Wilderness, surrounded by Monte Cristo, Kyes and Columbia peaks. It is fed by the Columbia Glacier to the northwest and drained by Troublesome Creek. The glacier's cold, silt-filled meltwater gives the lake its turquoise-green colour, a prime example of a rock-flour lake.

Blanca Lake lies in a basin beneath Monte Cristo, Kyes and Columbia peaks, fed by the Columbia Glacier and drained by Troublesome Creek. Its turquoise colour comes from cold, silt-laden glacial meltwater, making it a textbook rock-flour lake. The surrounding basin was shaped by glacial action, and the lake is now within the Henry M. Jackson Wilderness.

The lake's name, Spanish for "white," contrasts with its turquoise-green water, coloured by rock flour from the Columbia Glacier. Hikers reach it via the Blanca Lake Trail, which climbs from 579 m at the trailhead past Virgin Lake at 1,402 m before dropping 183 m to the shore.

The Blanca Lake Trail starts at 1,900 ft (579 m) and climbs 2,700 ft (823 m) over 3 mi (4.8 km) to a ridge, then passes Virgin Lake at 4,600 ft (1,402 m) before dropping 600 ft (183 m) over 0.5 mi (0.8 km) to the lake. A washout has closed Forest Road 63, adding about 4 mi (6.4 km) to the usual 9 mi (14.4 km) route. Snow usually limits easy access to July through October or November.

The turquoise colour comes from rock flour: cold, silt-filled meltwater from the Columbia Glacier on the northwest side. The lake drains into Troublesome Creek, a tributary of the North Fork Skykomish River. Hikers reach it only on foot, and the trail drops 183 m over the last 0.8 km from Virgin Lake.