Tricos will be on the water early this month when the day is warm. They'll start early in the morning and continue until noon or later. Size 16-18 adult caddis with tan or olive bodies should also be on the water in the evenings. Some size 18 black caddis may also be present.
For many anglers, the cranefly hatch is a special event here. The action starts in the morning, takes a siesta, then picks up again in the evening. Skate a Mackay Special or Darbee Cranefly across the surface. For another take on cranefly patterns see Tying Adult Cranefly Patterns.
Beetle, hopper, and ant patterns can do well until the first frosts bring terrestrial activity to a screeching halt.
Expect blue-winged olives by mid-month, maybe earlier. October caddis may make an appearance, too.
Be ready to change your tactics. If something works for a while, then stops working, change your approach instead of doggedly sticking with what worked an hour ago.
For more on September tactics and flies, see the Rivers in General forecast