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Thompson Lake via Mount Defiance

Snoqualmie Region


Snoqualmie Region -- Snoqualmie Pass
View map below


19.8 miles, roundtrip


Highest Point: 4200 ft.


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WTA worked here: 2018

Parking Pass/Entry Fee

Northwest Forest Pass

Unbeknownst to many, there's a beautiful lake tucked into the forests on the west slopes of Mount Defiance. Thompson Lake provides a great destination for day hikers or overnighters in the Alpine Lakes Wilderness. You may even find solitude here, just off the I-90 corridor. But that solitude comes at a price.

The trail up to Mount Defiance can be trying, especially in the height of summer. Climbing moderately, and then steeply away from Mason Lake, hikers are eventually rewarded with fields full of flowers and a gorgeous panorama from the summit of Defiance. But at the end of the traverse just below the summit, a little bootpath descends quietly into the forest.

This is the trail to Thomspon Lake: a large, scenic lake with nice alpine boulder fields and great views of the interior of Alpine Lakes Wilderness and Pratt river valley. Here, a number of small forested islands catch the sunlight in morning and evening, providing a relaxing panorama if you've chosen to camp.

From the traverse on Defiance, follow the narrow, somewhat brushy trail over to the north side of Defiance Ridge. 2.6 miles of ridgeline traverse bring you to yet another backbone, where you may be able to spot Spider Lake and creek in the basin to the southeast.

But you're heading to the northwest. Thompson Lake lies at the base of several steep switchbacks, just 0.8 miles away.

The lake has some good campsites. The main area is across the inlet stream just after you cross the stream on some logs when you finally get down the switchbacks. The trail around the lake passes a junction with trail 1009A and 0.3 miles past that junction are some smaller sites.

WTA Pro Tip: Because this trail starts from the very popular Ira Spring Trailhead, consider arranging a pick up or drop-off for this hike, particularly if you're doing an overnight


Thompson Lake via Mount Defiance

Map & Directions

Co-ordinates: 47.4248, -121.5835 Open map in new window


Snoqualmie Region -- Snoqualmie Pass

Thompson Lake (#1009.1), Mount Defiance (#1009), Ira Spring (#1038)

Mt. Baker-Snoqualmie National Forest, Snoqualmie Ranger District

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Getting There

Head east on I-90. Some 44 miles west of Seattle, take Exit 45 (Forest Road 9030.) The pavement ends in a quarter mile, and beyond that there may be significant potholes. At a fork 0.8 miles from I-90 take the left branch onto Road 9031. The right branch, Road 9030, goes to the Talapus Lake trailhead. At 3.8 miles from I-90, reach the large parking area for the Ira Spring Trail (#1038.) A privy is available, but no regular water source. A Northwest Forest Pass is required.

Be aware that this is a very popular trailhead; parking can be quite crowded here on a weekend. Take heed of the No Parking areas -- the Forest Service regularly checks this area and will issue tickets for violations.

Parking Pass/Entry Fee

Northwest Forest Pass

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Thompson Lake via Mount Defiance

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