From the trailhead at the logging road turnaround (800'), hike the logging trail for about 1 mile (20 min) and turn right on an unobstructed logging trail spur. This road quickly narrows to a trail which goes first north then turns west. after about a mile on this trail (20 min) and 550 ft. elevation gain from the TH, look for the sign marked "Teneriffe Falls" and take it. This recently improved trail follows switchbacks in and out of a talus field until it reaches Teneriffe Falls (Kamikaze Falls) at about 2550'. Just before reaching the falls, look for a climbers trail to the right. Follow this trail as it climbs 400' to a saddle at about 2950' and turn left directly up the ridge. There may be several bootpacks but they typically converge and diverge up the ridge. At about 4300' the trail moves leftward and through a high meadow and through a rock band. After passing through a last stand of trees, the summit knob at 4788' is a short scramble beyond the trees. On the descent take care to follow the path up as it is possible to stray onto the wrong ridge. Alternatively, from the summit it is possible to drop off the summit and hike north westerly along a ridge until intersecting with the terminus of an old logging road. this logging road can be followed to the TH, or can be used to connect a Teneriffe - Si traverse hike.
Trip starts from the main Mt Si TH, goes past a waterfall and over to the road, where we follow the road up to Teneriffe; there's a fun forested ridge walk and the final ascent to Teneriffe is very steep.
NOTE: There was 6+ inches of snow at 4300 ft last Saturday; it has warmed up but I expect there will likely be some snow on the summit of Teneriffe still.