September is a great time to be on the Bighorn. The crowds have thinned out, Black caddis hatch in the evenings, and the weather is very nice. I got married in Montana and spent the whole month of September on the Bighorn as our honeymoon. We went back two years later and spent another September on the Bighorn. Here are the flies that you will have mucho success with:
Pink soft hackle sow bugs #16-18
Tan soft hackle sow bugs #16-18
Orange scuds #16-18
Black,red,cream thread midge larva #18-22
Black cdc caddis with green bodies #18 (both the emerger and the dry)
Pink Ray Charles #16-18
Gray Ray Charles #16-18
If you have these flies on hand you will catch fish all day long. During September the flow will be around 1500 cfs and the fish will be stacked in the seams of the fastest water. And they are HOT this time of year.
Let me know if you have any questions about anything.
DBunch