Getting to Lake SereneAccess to the trailhead is about a quarter-mile off of U.S. Hwy 2 (Stevens Pass Highway). The trailhead you want is for the Lake Serene Trail No. 1068. A half-mile west of the turn off to the town of Index (this turn off is at the Index Cafe) on the south side of the Skykomish River near the bridge, a road turns off and continues a short distance to a fork. The right fork goes to the trailhead (c. 600 ft). Beware of car prowls at this trailhead!
This is the new trail. The old trail was a steep climber's path through wet, mossy forest and slabby rocks. The new trail is 3.5 miles long and gains 1,900 ft to the lake (2,521 ft).
Note: a more in-depth presentation of this route can be found in my trip report.
Approach to the saddle beyond the lakeAfter taking the new trail to the lake's outlet, circle around the lake on its west side (the east side is more cliffy and cumbersome). About one quarter of the way around you will pass some fantastic house-sized boulders. Depending on the time of year, you may have to traverse steep snow or talus. Beware of avalanche and rockfall danger traversing below the East Faces. Your objective is the 3,050-ft saddle above the SE side of the lake. It is about a mile to get from the outlet to the saddle. At the south end of the lake begin making a rising traverse to the saddle. There is brush intermixed with talus through here (moderate bushwhacking). The saddle is largely brush-free. Are you ready for it because here it comes.
The East Ridge above the lakePray you find the climber's path that leads up on the ridge southwest of the saddle. This is the (lower) East Ridge of Index. The most formidable (read: exasperating) climbing is for the first 500 feet on this ridge. It can easily become a brush bash. There are rock outcrops along the ridge with wet slabs the general trend on the south side. Basically, go up the spine or to the north side as dictated by the brush. Maybe 200 feet up from the saddle there is a 10-ft rock step with definite exposure below. This is about where the permanent climber's path starts. The rock step has roots and limbs above for green belaying but it is definitely an attention-getter. A long runner would make it safer. Once above this step, the going is largely on path through encroaching brush until the ridge opens up at c. 3,800 ft.
The Hourglass GullyAfter the East Ridge opens up you will see that it terminates in a rough headwall. On the left about a quarter-mile to the SSW the headwall corners at a buttress. That corner (c. 4,200 ft) is your next objective. Round the corner and ascend due west into the narrowing constriction of the gully (c. 5,000 ft). The narrowest section is the crux of this climb in summer due to a 30-ft Class-5 step. In winter and early spring the snow will provide a bridge up this step. In late spring-early summer, there will probably be a moat. Once above the constriction two couloirs will present themselves to you: a wide one on the left and a narrow (possibly corniced) one on the right. Ascend the left one to the 5,550-ft saddle.
In the event that you are climbing this gully in the summer when the snow bridge is gone, you will be faced with two possibilites: a wet trickling waterfall on the left and an awkward chimney on the right. For the former, it may be possible to scratch and claw your way up the far left side. The middle of the waterfall is overhanging. The left wall would be hard Class 5. The latter chimney is cleaved in two by a rock. Squeeze up one of these clefts (can't remember if it's the left or right cleft; you'll know when you get there). The cleft is Class 4 verging on Class 5. About 20 feet up, you can make a sketchy Class-5 traverse left across a face back to above the trickling waterfall. Beware of wet rock. The other alternative is to continue up the chimney another 20 feet to a grassy ledge on the left. The chimney continuance is probably some level of Class 5. I don't want to conjecture beyond that and whether or not the grassy ledge has an exit.
The rest of the way to the topFrom the 5,550-ft saddle to the summit it is all easy Class 2 (one short, steep snowslope if snowcovered). Immediately above the saddle is a rounded knoll (or snow dome in winter-spring). Continue along the dome then the crest to just below the massive summit blocks. If winter/spring, admire the huge cornice (no danger to you). How to climb the summit blocks? No worries. Simply contour around the west side of the rocks until they end. The west finish is open heather/snow. There is a summit register.
DescendingIf not doing a Index-Persis traverse, the descent route is the ascent route. Downclimb or glissade the hourglass gully. If summer, rappel the constriction (I don't know about anchor availability). At the base of the gully (4,200 ft) there are two descent options: 1) back along the lower East Ridge (will probably require a rappel), or 2) down into the West Fork Index Creek drainage thence up to the 3,050-ft saddle.
Option 1: The nature of the lower East Ridge is such that a rappel is much safer and maybe faster too. This would especially be the case if there is snow on the ridge. On the way up there are enough things to grab on to that the climbing is manageable unroped (this obviously depends on your experience level). In May 2002 we did one long double-rappel down the slabbier side.
Option 2: This is a great option--especially if there is ample snowcover. Routefinding is key, though, because of a cliff band far below the Hourglass Gully at ~3,200 ft. The idea is to continue down to the valley head (c. 2,600 ft) 0.8 miles NW of Mud Lake then turn left (north) and climb up to the saddle. 400 feet of extra climbing but the exposure is much less (unless you find yourself hampered by the aforementioned cliff band). To avoid the cliff band, at 4,200 ft veer right and angle in a southeasterly direction for about 0.4 miles before heading straight downhill. You can see this lower-angle slope on maps. It is sparsely treed. It may be possible to veer right only half the distance to save time. The best advice here is to observe this possible descent route while climbing along the East Ridge at the 3,800-ft level. You should be able to see a route if there is one to your liking.
Essential GearEarly season: ice axe, crampons if snow is going to be hard, possibly snowshoes if snow is going to be soft
Late season: small alpine rack, maybe a knifeblade or two
All seasons: helmet, rain gear (wet brush sucks), at least a 30m rope (50m rope better), rappel device