Primus Peak/Borealis Glacier

Primus Peak via the Borealis Glacier is a Grade II, class 2-3 climb.

Getting There

Drive I-5 to Exit 232 (Cook Road) at Burlington, turning east to Sedro Wooley and SR 20. Continue 47 mi to Marblemount for trip permits for Klawatti Zone at Park Ranger Station. Continue to Colonial Creek and park at the Thunder Creek trailhead, 1,200 ft.


Hike the Thunder Creek Trail for approximately 6 mi, making sure to stay on this trail at the junction with the Panther Creek Trail at about 1.6 mi in. Continue on to McAllister Camp. The campground is located at a confluence of two valleys — McAllister Creek on the west and Thunder Creek on the south — just after crossing Thunder Creek on a good bridge.

The ridge is long, cliffy, and brushy but manageable. Follow camp way trails heading up towards the ridge to find the start of the faint climber's trail that follows most of the ridge but it is easy to lose in a couple of places. With careful routefinding one can avoid anything more than a few class 3 sections.

The trickiest obstacle is a small cliffy section around 4,000 ft foot elevation. It is easier to find on the way up then down — consider taking a GPS way point.

The second tricky section is located between a rocky open spot at 4,750 ft and the upper heather slopes (5,000 ft). Continue up the ridge for a total of just over 2 miles to the toe of the Borealis Glacier at 6,000 ft. There is good camping here. Allow an entire day to make this camp.


From camp traverse around the right (northwest) side of the lake at the toe of the lower Borealis Glacier, scrambling on rocks as needed until you can get around and above the like. Ascend gentle slopes to climber's right until you can cut left and gain the upper Borealis Glacier, heading above cliff bands and an obvious icefall. Traverse up and left toward Tricouni and cut up the col between Tricouni and Primus (Lucky Pass, 7,200 ft). From the col, ascend the east ridge of Primus (class 2-3).


Descend the climbing route.


Seattle to Trailhead 2.5
Trailhead to Camp 7-9 4,800 ~8
Camp to Summit 3-4 2,500 ~1.5
Summit to Trailhead 9-11 ~9.5


Ice axe, crampons, standard glacier travel gear.


This is a strenuous climb as a two day trip. A  three day trip would be more moderate and also allow for tagging Tricouni on the second day.

Recommended time frame is mid- to late summer.

  • Suitable Activities: Climbing
  • Climbing Category: Basic Alpine
  • Seasons: July, August
  • Weather: View weather forecast.
  • Difficulty: Basic Alpine Climb
  • Length: 19.0 mi
  • Elevation Gain: 7,300 ft
  • 8,508 ft
  • Land Manager: North Cascades National Park
    Stephen Mather Wilderness
  • Parking Permit Required: None
  • Recommended Party Size: 6
  • Maximum Party Size: 12
  • USGS Forbidden Peak

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