Free Resource · Updated 2026
The complete fly hatch chart for Wyoming's legendary trout rivers. From world-class tailwaters like Gray Reef and the Bighorn to the Salmonfly spectacle on the Snake River and the unique thermal Firehole in Yellowstone — select your river for peak hatch timing, fly pattern recommendations, and current month highlights for 2026.
Wyoming Hatch Calendar — Quick Reference
Wyoming Rivers
North Platte Gray Reef · Green River · Bighorn River
Cold dam releases from Alcova, Flaming Gorge, and Yellowtail dams create world-class trout fisheries that produce year-round. Midges and BWOs fire through winter on overcast days. PMDs and Caddis dominate summer. Because tailwater temperatures are regulated, hatches are more predictable than freestone rivers — and the trout are enormous. Gray Reef near Casper is consistently ranked among the top trout fisheries in North America.
Firehole River · Yellowstone River · Madison (upper)
Unique geothermal springs warm the Firehole and create atypical early-season fishing conditions. Wild cutthroat dominate the Yellowstone and Lamar Valley with spectacular dry fly fishing for large fish in a wilderness setting. Most Park waters open late May or July 15 depending on the section. The compressed season means hatches fire intensely — particularly PMDs and Caddis in July and Tricos in August on the Firehole and Yellowstone.
Snake River · Shoshone River · New Fork River
Freestone rivers fed by Teton and Wind River snowmelt. Runoff clears by late May on the Snake, triggering the Salmonfly hatch — one of the most spectacular dry fly events in the Rockies. Golden Stones follow into July. July through August is prime hopper season, with cutthroat and brown trout crashing foam flies fished tight to cut banks. Fall Mahogany Dun and BWO fishing runs through October on all three systems.
The Why Behind the Chart
Pteronarcys californica
Wyoming's most anticipated dry fly event — giant stoneflies up to 2.5 inches long that drive large cutthroat and brown trout into a feeding frenzy. The hatch progresses upriver as water temperatures warm following spring runoff. On the Snake River below Jackson, peak fishing is often the last week of May through mid-June. Watch for the bugs on streamside vegetation and fish the banks hard — these are ambush-point fish crashing large foam patterns. The Shoshone River near Cody and sections of the North Platte also produce strong Salmonfly fishing.
Recommended: #4–6 Stimulator, Chubby Chernobyl, Kaufmann Stone
Hesperoperla pacifica
The Golden Stone follows the Salmonfly by 2–3 weeks and often provides even better fishing — smaller fish are less spooked and the hatch window is longer. Golden Stones are present on all of Wyoming's major freestone rivers, including the Snake, Shoshone, and New Fork. They hatch throughout the day but the best action is typically late afternoon as adults return to lay eggs. A tan or golden Stimulator or Elk Hair Stone in #6–8 is essential through June and into early July.
Recommended: #6–8 Golden Stimulator, Elk Hair Stone, Copper John dropper
Ephemerella inermis
Wyoming's most reliable summer mayfly hatch and the foundation of dry fly fishing on tailwaters. PMDs hatch from mid-morning into early afternoon, bringing selective trout to the surface on the Green River, Gray Reef, and Bighorn. On freestone rivers like the Snake and Firehole, the hatch fires later in the morning. Fish the sparkle dun or cripple — trout key on emergers in the film. The Bighorn's PMD hatch in July and August is renowned for producing some of the most technical and rewarding dry fly fishing in the country.
Recommended: #16–18 PMD Sparkle Dun, CDC Emerger, Comparadun
Hydropsyche sp. / Brachycentrus sp.
Caddis are the workhorse hatch across all of Wyoming's river types from June through August. Tan and olive caddis dominate the Snake and freestone drainages; the Green River tailwater has exceptional caddis populations that fish throughout the season. Evening caddis egg-laying activity on the Firehole and Yellowstone rivers can produce some of the best surface action of the day. An X-Caddis or Elk Hair Caddis with a soft-hackle dropper covers the full hatch cycle from emerger to adult.
Recommended: #14–16 Elk Hair Caddis, X-Caddis, Partridge Soft Hackle
Tricorythodes sp.
Wyoming's most technical dry fly challenge — tiny spent spinners that fall at first light, often over by 9am. The Bighorn River is famous for massive Trico spinner falls in August that produce extraordinary numbers of rising fish but require 6X–7X tippet and precise presentation. The Firehole and Yellowstone rivers within the Park also host good Trico activity. Approach rising fish low and slow, target individual risers, and watch the drift carefully — refusals are more common than takes until you get the presentation right.
Recommended: #22–26 Trico Spinner, CDC Trico, Parachute Trico
Baetis sp.
Wyoming's most reliable early-season and late-season hatch — and the bread-and-butter of tailwater fishing year-round. BWOs hatch on overcast, drizzly days when light levels are low. On Gray Reef, the Miracle Mile, and the Bighorn, BWOs fish through winter even when ice lines the banks. Spring BWOs in March–April signal the start of the dry fly season. Fall BWOs return in September–October across all river types. When the weather looks miserable, think BWO — that's exactly when they're best.
Recommended: #18–22 Sparkle Dun, RS2, Parachute Adams
Wyoming's hatch calendar begins with Midges and Blue-Winged Olives on tailwaters like Gray Reef and the Green River in early spring — often fishing well on overcast days from March onward. The Firehole River in Yellowstone benefits from geothermal spring water that keeps temperatures fishable when other rivers are still locked in winter. Spring BWOs peak in April on all tailwater systems.
The Salmonfly and Golden Stone hatches on the Snake River and Shoshone in late May and June are among the most spectacular dry fly events in the Rocky Mountains. Thousands of giant stoneflies take wing while cutthroat trout crash the banks — this is bucket-list fishing that anglers plan around for years. PMDs follow in July on both freestone and tailwater rivers, providing more technical but equally rewarding opportunities across all of Wyoming's best waters.
Wyoming's hopper fishing from July through September is legendary — big foam flies fished tight to cut banks produce explosive strikes from large cutthroats on the Snake and New Fork. The Trico spinner fall on the Bighorn River in August is one of the most remarkable sights in angling. Fall brings Mahogany Duns and BWOs through October. Use FlyFishFinder's live gauge data to time your trips when flows and temperatures align.
See Live Wyoming River Conditions →Common Questions
The Salmonfly hatch on the Snake River below Jackson typically runs from late May through mid-June, progressing upriver as water temperatures rise. Peak hatch timing depends heavily on spring runoff — in high water years it can be pushed back into late June. The Shoshone River in Cody also gets a good Salmonfly hatch. Watch for giant stoneflies on streamside vegetation as your first signal — fish the banks hard with a #4–6 Stimulator when the bugs are in the air.
July is Wyoming's prime dry fly month. PMD Sparkle Duns (#16–18) work on most rivers morning into afternoon. Hoppers (#10–12) fished tight to cut banks produce explosive strikes on the Snake and New Fork. Golden Stones (#6–8) remain effective early in the month. On tailwaters like Gray Reef and the Bighorn, Caddis and Trico patterns also produce. Bring a full box — July offers more dry fly options than any other month in Wyoming.
Gray Reef is a dam-release tailwater below Alcova Reservoir near Casper — consistently rated among the top 10 trout fisheries in North America. Cold, clear flows year-round support enormous rainbow and brown trout. Midges and BWOs fish through winter. PMDs and Caddis dominate summer. Because it's a tailwater, hatches are more predictable and less weather-dependent than freestone rivers. Flows are managed for fishing quality, making this a reliable destination regardless of season.
Wyoming tailwaters (Gray Reef, Miracle Mile, Green River, Bighorn) fish year-round with reliable Midge and BWO hatches even in winter. PMDs and Caddis show in summer. Freestone rivers (Snake, Shoshone, New Fork) depend on snowmelt runoff clearing — hatches typically don't fire until late May or June when flows drop and warm. The Yellowstone Park rivers open July 15 with a compressed but spectacular summer season.
Most Wyoming rivers outside Yellowstone National Park are open year-round or from January 1. The Firehole, Madison, and Yellowstone rivers within Yellowstone National Park typically open on the Saturday of Memorial Day weekend (late May) for most sections, with some trophy sections not opening until July 15. The Snake River below Jackson opens in April. Always check current Wyoming Game and Fish regulations before your trip — specific sections have different open dates.
July is Wyoming's peak dry fly month — PMDs, Caddis, hoppers, and Golden Stones all overlap for outstanding surface action on most rivers. June brings the Salmonfly spectacle on the Snake and Shoshone. Tailwaters like Gray Reef and the Bighorn fish well year-round, making January through March viable with Midges and BWOs. Fall (September–October) offers excellent Trico and BWO fishing with uncrowded rivers and elk bugling in the background.
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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