Free Resource · Updated 2026
The complete fly hatch chart for Idaho's legendary spring creeks, freestone rivers, and remote mountain streams. From Henry's Fork's world-famous PMD and Green Drake hatches to the Salmonfly spectacle on the South Fork Snake and Kelly Creek's wild cutthroat — select your stream below for peak hatch timing, fly pattern recommendations, and current month highlights for 2026.
Idaho Hatch Calendar — Quick Reference
Idaho Streams
Henry's Fork · Silver Creek
Stable groundwater temperatures and clear, slow currents create the most demanding dry fly conditions in Idaho. Henry's Fork Railroad Ranch and Silver Creek hold large, highly selective trout that require precise presentations and fine tippets. PMDs, Callibaetis, and Trico hatches define the summer season. Hatches arrive earlier and last longer than freestone streams. The challenge is high, but so are the rewards.
South Fork Snake · Teton River · Big Wood
Larger, faster water with more diverse hatches anchored by the spectacular Salmonfly and Golden Stone emergences in May and June. Flows are snowmelt-dependent — high water years can push the Salmonfly hatch progress upriver by 2–3 weeks. Once flows drop, PMDs and caddis provide consistent dry fly action through summer. These rivers fish best when water is dropping and clearing after runoff.
Kelly Creek · St. Joe River · South Fork Boise
Idaho's most remote and wilderness-adjacent fisheries. Kelly Creek and the St. Joe hold wild Westslope cutthroat that are far less pressured than fish on famous rivers. Salmonfly and caddis hatches drive most surface activity in June and July. The South Fork Boise is a tailwater exception — cold dam releases support year-round fishing with midges and BWOs anchoring the off-season. Access to remote streams requires planning but rewards solitude.
The Why Behind the Chart
Pteronarcys californica
Idaho's most dramatic hatch and one of the great dry fly events in western fly fishing. Giant stoneflies — up to 3 inches long — emerge from larger freestone rivers and trigger explosive surface feeding from the biggest trout in the system. The hatch progresses upstream as water temps warm, moving roughly 5–10 miles per day. South Fork Snake and St. Joe are premier destinations. Chase the hatch front for the brief window when fish are completely committed to the surface — it's unlike anything else in fly fishing.
Recommended: #4–6 Chernobyl Ant, Sofa Pillow, Stimulator
Ephemerella infrequens
Idaho's most important dry fly mayfly hatch and the centerpiece of the Henry's Fork experience. PMDs fire from late morning through early afternoon throughout the summer, producing the most consistent sustained surface feeding of the season. On Henry's Fork Railroad Ranch, PMD hatches bring large rainbow trout to the surface in the flat, weed-laden current — demanding precise casts and drag-free drifts on 5X tippet. On Silver Creek, the hatch is even more technical due to gin-clear water and wary fish.
Recommended: #16–18 PMD Comparadun, Sparkle Dun, CDC Emerger
Drunella grandis
A premier event on Henry's Fork and the Teton River, the Western Green Drake is the western counterpart to Pennsylvania's famous Ephemera guttulata — large, olive-bodied mayflies that bring big trout to the surface in the middle of the day. The hatch peaks on Henry's Fork in late June, coinciding with peak PMD activity for an extraordinary few weeks of dry fly opportunity. Trout respond aggressively to well-presented Green Drake imitations when the hatch is firing.
Recommended: #10–12 Green Drake Comparadun, Paradrake, CDC Drake
Callibaetis sp.
The signature hatch of slow, weedy spring creek water — especially Henry's Fork Railroad Ranch and Silver Creek. Callibaetis emerge from mid-morning through afternoon throughout summer, with multiple broods extending the season well into September. These speckled-winged mayflies hatch in the film and trout rise selectively and steadily to both emergers and duns. Callibaetis spinner falls at dusk can produce the best dry fly fishing of the day on Henry's Fork in late summer.
Recommended: #14–16 Callibaetis Comparadun, Parachute Adams, Sparkle Dun
Tricorythodes sp.
A summer morning staple on Henry's Fork and Silver Creek. Trico spinner falls happen at first light — often intense but short-lived, usually over by 9am. Trout sip spent spinners in flat water with maddening calm, requiring long leaders, fine tippet, and exact fly placement. Henry's Fork Trico fishing in August rivals the most technical hatch fishing anywhere in the country. Approach low, target individual risers, and be prepared for refusals on imperfect drifts.
Recommended: #20–24 Trico Spinner, CDC Trico, Black Beauty
Baetis sp.
Idaho's most reliable shoulder-season hatch — present on every stream type from tailwaters to remote mountain creeks, most dependably on overcast and drizzly days. Spring BWOs arrive in March on warmer streams and persist through May. Fall emergences in September through November often produce the most consistent surface fishing of the season as water temps cool. On the South Fork Boise tailwater, BWOs can hatch year-round and provide the foundation of winter dry fly action.
Recommended: #18–22 Sparkle Dun, CDC Emerger, RS2
Idaho is home to some of the most celebrated dry fly water in North America. Henry's Fork of the Snake River — particularly the Railroad Ranch section — is world-famous for its demanding PMD, Green Drake, Callibaetis, and Trico hatches that test presentation skills against large, selective rainbow trout. Silver Creek near Sun Valley offers a similar challenge on spring creek water that demands fine tippets and technical drifts.
The Salmonfly hatch on Idaho's larger freestone rivers is one of the great spectacles in western fly fishing. The South Fork Snake, St. Joe, and Big Wood explode with surface activity when Pteronarcys californica — giant stoneflies up to three inches long — begin emerging in late May. The hatch moves upstream through June, and chasing the hatch front is a tradition among Idaho anglers. Golden Stoneflies follow the Salmonfly for another two to three weeks of big attractor dry fly action.
PMD hatches anchor the summer schedule on most Idaho trout streams from May through August. Callibaetis and Trico provide technical summer fishing on slow-water streams. Fall BWOs and Autumn Caddis extend the season on all stream types through October. Use FlyFishFinder to track flows and find the optimal window for chasing Idaho's famous hatches.
See Live Idaho River Conditions →Common Questions
Pale Morning Duns on Henry's Fork begin in late May and run through August, peaking in June and July on the Railroad Ranch section. The hatch fires morning through early afternoon. Henry's Fork is legendary for selective trout — 5X tippet and drag-free drifts on long leaders are essential. The flat, clear water of the Ranch section amplifies both the challenge and the reward.
Silver Creek near Sun Valley is one of North America's most technically demanding spring creeks. Crystal-clear, slow water means trout scrutinize every fly. Callibaetis and PMDs are the signature hatches, with Trico spinner falls providing early morning summer action. Use 12–15 foot leaders and 5X to 6X tippet. The Nature Conservancy section is catch-and-release and holds large, educated trout.
The Salmonfly hatch typically runs late May through mid-June on Idaho's larger freestone rivers, progressing upstream as water temps warm — roughly 5–10 miles per day. South Fork Snake and St. Joe are premier destinations. Locals track the hatch front carefully for the brief window when the biggest trout are actively rising to these large stoneflies.
June is Idaho's best month for diverse dry fly action. On big water like the South Fork Snake, carry Golden Stonefly patterns (#6–8) and large Elk Hair Caddis. On Henry's Fork, PMD Comparaduns (#16–18) and Western Green Drake imitations (#10–12) are essential. A Parachute Adams covers situations between hatches on any Idaho stream.
Kelly Creek in the Clearwater drainage is remote, pristine, and holds wild Westslope cutthroat that respond readily to dry flies — an Elk Hair Caddis or Royal Wulff often outperforms exact imitations. The Salmonfly and Golden Stone hatches in late May through June are the peak windows, but attractor dry fly fishing is good all summer. Access requires forest road travel and sees far fewer anglers than famous rivers.
June offers the broadest dry fly opportunities — Salmonfly and Golden Stone hatches on big rivers, PMDs on Henry's Fork and Silver Creek, and Green Drakes beginning. July and August provide consistent PMD, Callibaetis, and Trico action. September and October bring outstanding BWO fishing with fall colors and fewer crowds. Henry's Fork Railroad Ranch is best in June–July before weed growth peaks.
FlyFishFinder combines hatch knowledge with live gauge alerts, Prime condition indicators, and real angler intel — so you show up on the right day, not the wrong one.
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