In the summer, terrestrial patterns such as ants, beetles and inchworms are very effective.
Using these is often more effective than trying to fish the tiny flies.
In the summer, patterns that imitate green inchworms are probably the most effective patterns of all. In the fly shops these are sometimes called Inchworms, but more often referred to as the Green Weenie.
Also, tan caddis, in sizes 14, 16, and 18 are good all through the season, including the summer. The size I use the most is size 16.
Also, for fishing the evening rise, when you see trout rising at dusk, but aren't sure what they are rising to, try using Rusty Spinners, or Sulphur spinners, size 16.