If you only plan one hatch strategy for October, make it Blue-Winged Olives. BWOs are the signature fall hatch nationwide — #18–22 mayflies that hatch mid-day as the weather cools, from September into November. When everything else is winding down, BWOs are winding up.
Fish the gray days
Cloudy, cool, drizzly days are BWO days. Overcast skies stretch the hatch and bring more fish up. A cold front with steady cloud cover is the best dry-fly weather October offers — plan around it, not against it.
Be there mid-day
The hatch peaks in the middle of the day, roughly 11 to 2. You don’t need to set an alarm. Show up late morning, rig for nymphs first, and switch to dries when you see noses.
Carry the whole progression
Nymphs and emergers in #20–22 cover the fish eating below the surface; dun patterns in #18–22 cover the top. Olive and gray bodies are the standard colors. On heavily pressured water, a CDC emerger or a cripple pattern often outfishes a perfect dun.
Where to look
BWOs matter across the trout map — Colorado freestones and tailwaters, Idaho’s Silver Creek and Fall River, the Upper Owens in the Sierra, and spring creeks and tailwaters in the East. Slow flats, tailouts, and soft seams hold the risers.
The beauty of the October BWO hatch is its reliability. It happens on schedule, in the middle of the day, on the kind of weather nobody else bothers to fish. That’s about as good as fall dry-fly fishing gets.
