Rainbow Lake Trail begins and ends at trail junctions deep in the Lassen Volcanic National Park backcountry. Therefore, it is typically a section of a longer run. As described here, Rainbow Lake Trail begins on the west side of Snag Lake at a well-marked trail junction with Butte Lake to Snag Lake Trail (West)
and Grassy Creek to Snag Lake
Trail. This trail junction is in an open area covered with deadfall between widely spaced pines, very close to Snag Lake. To the east, across Snag Lake, Mt. Hoffman rises to 7,833 feet. To the west is the bench that Rainbow Lake Trail climbs up on.
Although Rainbow Lake Trail begins in an open area, it soon enters the pine forest with its low ground cover. Almost immediately the trail starts climbing, following a small seasonal stream valley that is to the left (south of the trail). As the trail climbs there are great views of Mt. Hoffman for a while, but eventually it can no longer be seen through all the trees. This climb lasts for about a mile with a few somewhat steep sections.
At about the 1.0 mile mark, the climb eases, views of Lassen Peak
emerge to the west-southwest, and by the 1.2 mile mark the highest point of Rainbow Lake Trail is reached. The pines are thinner here on this high bench in the center of the park. At about the 1.4 mile mark the trail begins a very gradual descent for about a half mile to arrive at the east end of Rainbow Lake. The forest becomes thicker as Rainbow Lake is reached.
After 2.0 miles Rainbow Lake Trail ends on the north shore of Rainbow Lake, at a trail junction with Rainbow Lake to Nobles Trail
Pine forest with low ground cover between the trees. Wildflowers. Shy deer as evidenced by tracks.