As stated by others, as fall comes, I would shift my attention from streams draining primarily from above the snow-line, to either downstream areas, or streams that drain from lower elevations. You can still fish dries, especially October caddis. A lot of the lower draining streams will fish through November, if they're open. And if they're below anadromous barriers, they're likely going to have sea run cutts, which will also take dries, dead drifted or skated.
If continuing to fish the resident trout streams is your game it is all about stream temperatures. As the temperatures drop into the mid-40s and below the fish change their behavior. The juvenile and smaller adult trout (stuff under say about 10 inches) leave their usual summer/feeding haunts and seeking out safe areas in which to over winter. Those areas typically in complex habitat features - the mains into the large substrate, log jams, root wads, rip-rap, etc. Those smaller fish will spend most of the winter in those habitats. With limited food resources the fish move into survival modes which in this case means refuge from the winter floods. The larger fish tend to move into the larger/deeper pools using that depth and slow currents as their refuge.
Accordingly one needs to adjust their fishing as dedicated by the fish's behavior. This means as we move into the fall the fishing will move downstream (the higher headwater areas will cool sooner than the larger lower reaches). That means that say a 6 weeks from now the Yakima at Ellensburg will fish better at Cle Elum. Once the temperatures drop shift your focus to that larger/deeper water where4 deeply fished nymphs and streamers will be your likely choice. There still can still infrequent bug hatches that may stimulated a "bit". The good news while fishing will be tougher will much lower catch rates the average size will increase dramatically (more apt to find those hatches later in the winter or early spring).
The other thing that will happen is by late November into February the mountain whitefish while collect in the specific large pools for pre-spawn/spawn/post spawn aggregations. It may take some time to find those aggregations; it is not uncommon for all the fish in several miles of year to collect in a single pool. The good news is that the fish will use those same areas year to year unless there are major changes in the river channel. Those white fish can be taken on deeply fished nymphs (usually smallish sized flies) and every once in awhile on dries during an afternoon BWO hatch.
As suggested by the others the alternative is to get in another game; stillwater, steelhead or one of my favorites bull trout.
As it will be getting cooler I will gradually put my trout setup away and head out to the big rivers with my two hander and slam some steelhead and salmon well................atleast try. I am the rookie here after all.