The route begins at the Wild Basin ranger station, which has ample parking. A timed entry permit is required between 9pm-5pm, but the parking lot was already full at 7:30am. I had to go back down about a half mile where there are some overflow lots. The trail is well marked, and clear as of September of 2025. The trail to Thunder lake splits off the busier Ouzel falls trail after a couple of miles. From here, it’s a narrow but well established trail. I saw very few people between this turn off and Thunder lake, despite it being a busy Saturday. I was struggling with the altitude and a lingering cold, but with the beautiful foliage I was able to run/walk my way up. On the way up I noticed some fish in the pools below the bridge over the St Vrain creek just below Thunder lake. From there, it was a pleasant run up to Thunder Lake. Despite seeing many fish rising to the surface at the lake, and getting multiple hookups, I couldn’t set the hook properly. Disappointed, but on a schedule and with the clouds turning dark, I began to head down. I kept my rod assembled to fish at the pools at the bridge, I quickly hooked a small brook trout on a green midge, which was carefully photographed and released. Elated, I took a quick breather and ran down to the parking lot. Of course in the morning I didn’t begin my garmin until a solid quarter mile past the trailhead. The time from trailhead photo outbound to trailhead photo on the return is 4hrs 54mins.

Early on, there are some pools along the St Vrain before the trail diverges from the creek. Near the top, there’s a couple more spots on the St Vrain before the lake. There are a couple of turnoffs to other lakes, but I’m not familiar with them.