Fall Fly Fishing in Montana: Your Guide to the Best September–October Hatches

Late-Season Fly Fishing on the Clark Fork & Bitterroot Rivers

As summer fades into fall, the Clark Fork and Bitterroot Rivers in western Montana come alive with some of the year’s most rewarding fishing opportunities. September through October offers an incredible variety of hatches and feeding activity, with cooler weather, fewer crowds, and trout eager to bulk up before winter.

Hatches to WatchIn early fall, expect steady emergences of Tricos, Blue-Winged Olives, and Mahogany Duns. These insects thrive in the cooler mornings and overcast afternoons, creating ideal conditions for technical dry fly fishing. Tricos often bring pods of rising fish to gentle seams, while Blue-Winged Olives and Mahoganies produce aggressive surface takes, especially on cloudy days.

Hopper Season Isn’t OverDon’t stash your terrestrial box just yet—grasshopper fishing remains consistent right through October and, in some years, even into early November. Warm afternoons still bring hoppers into play, and trout will readily key in on these big meals, especially in slower bankside water or under overhanging vegetation.

Why Late Season is Special

• Less fishing pressure: The summer rush is gone, giving you more solitude.

• Hungry trout: Shorter days and dropping water temps push fish to feed heavily.

• Scenery: Golden cottonwoods, crisp mornings, and the first hints of snow in the mountains make for unforgettable days on the water.

• 
  

If you’re willing to dress for cooler mornings, late-season fly fishing on the Clark Fork and Bitterroot can deliver some of the most memorable days of the year. Whether you’re matching the hatch with tiny tricos or tempting a brown with a size 8 hopper, autumn in western Montana is a fly angler’s dream.