I fished there around the 3rd week of Sept, one year, and got some bites fishing in the lake off the mouth of Walnut Creek. I did end of catching a few fish @ the well known hole about 1/4 mile up from the mouth (it is no secret, and there were plenty of folks fishing all around that area. BUT, the water was very low and clear, and WARM; and I just tossed out spawnbags and watched them until a fish would pick them up, then would set the hook. I got a few @ Elk Creek that day, too; but decided to wait for colder weather before going back. I went back when it got cold, and landed about 25 Steelhead in a day.
Trout Run is closed to fishing all of the time. I doubt that you will catch Steelhead in the lake there, during Summer, unless the wind blows the warm water offshore - which must happen sometimes. But starting in late September, and until ice-up, you can really get into them off T. R.