Nymphs during the day such as Zug Bugs, Princes, dark stoneflies and PT's in sizes 12-14 have been eaten readily. I always drop a small baetis nymph off the back size 18-22. Some favorites are PT's, and red Copper Johns. Dead drift your nymphs through any likely runs and holes and swing your flies at the end of the drift. Hold the there for at least a few seconds, and then strip them back to you. You will get as many or more fish on the swing and retrieve. Work the entire river with your swing not just the end of the pool. When swinging nymphs it is beneficial to use yarn or my favorite a foam hopper or stimulator as an indicator. You will spook less fish and pick up some on the dry as well. One thing I like about this time of year is that with fish chasing swimming nymphs it is a great time to get beginners on the water and in to fish as presentations do not need to be perfect.
The last hour before dark has been the best fishing of the day however, has been the most exciting fishing. Fish have been looking at the surface and largely ignoring nymphs which is OK with me! Parachute Adams have been my fly of choice as I can see it in the low light and riffles. Epherons- White fly spinners have been around too so a white wulff or similar pattern will see some action. October Caddis will start to show up soon. That means orange will be another color to imitate both on the surface and below.
Bottom line is get on the water. This is prime time right now!