Free Resource · Updated 2026
Henry's Fork of the Snake River is one of the great trout fisheries in the American West. The Railroad Ranch section holds selective wild rainbow trout that see constant pressure and demand precise presentations. Green Drake hatches in late June are legendary. PMD and Trico hatches carry the summer months.
Henry's Fork Hatch Calendar — Quick Reference
Henry's Fork flows from Island Park Reservoir through some of the most productive trout water in Idaho. The Box Canyon below the dam runs fast and deep with large fish. The Railroad Ranch (also called the Harriman section) is flat, glassy, and famous for picky trout that study every fly with suspicion.
The Ranch section requires light tippet, long leaders, and careful wading to avoid spooking fish. Approach rises from downstream and present the fly with a drag-free drift. The fish here have been educated by decades of pressure and will refuse any pattern that does not match the hatch precisely.
Green Drake hatches in late June and early July are the signature event on Henry's Fork. PMDs and Tricos carry the summer into September. Caddis are most active in May and June in the faster water of Box Canyon. BWOs provide reliable fishing in spring and fall when other hatches slow.
See the full Idaho Fly Hatch Chart for hatch timing across all of Idaho's top trout streams.
Check Conditions Near Henry's ForkWhat to Fish
Green Drake hatches on Henry's Fork are among the most anticipated events in Western fly fishing. The hatch usually peaks in the last week of June on the Railroad Ranch. Large duns come off mid-morning and the trout rise freely but with precision. Match the dun exactly and present with a drag-free drift from downstream.
Recommended: #10-12 Parachute Green Drake, Harrop Dun
PMDs hatch reliably on Henry's Fork through the summer months. The Ranch section produces long, consistent PMD risers that are notoriously selective. Fish the dun and then the spinner as the day progresses. A well-tied Comparadun in size 16 or 18 is a good starting point. Long leaders and light tippet are essential.
Recommended: #16-18 Comparadun, CDC Dun
Trico spinner falls draw rising fish on Henry's Fork from July through September. The falls happen early, usually by 8 or 9 in the morning, and can be heavy. Fish stack up in the slow flats of the Ranch section sipping spent spinners. Tiny flies and fine tippet are required. A size 24 Trico in a spinner pattern is the standard.
Recommended: #22-26 Trico Spinner
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