Henry's Fork
Last Chance to Ashton · Railroad Ranch
E Idaho, USA
Open live forecast →Target species: Rainbow.
Stream gauge: 13055000. Flow and water temperature update on every refresh.
Weekly AI Outlook as of 06/05/26
At 1280 cfs, Henry's Fork is running perfect for the Ranch section with prime Green Drake conditions building. Water temps in the ideal 52-60°F range should trigger late afternoon emergers, especially with highs in the low 70s early week. The famous hatch window is here — position along the right banks of the Ranch and be patient. PMDs and Callibaetis are also active midday as warm-ups to the main event. Wind picks up mid-week which could scatter surface activity, but mornings will stay fishable.
- Flow: 1280 cfs — ideal Ranch conditions, crystal clear water in the sweet spot for wade fishing and technical presentations
- Hatches: Green Drake emergence primed for late afternoon to dark, PMDs midday, Callibaetis sporadic — size 10-12 Paradrakes essential
- Water Temp: 52-60°F range perfect for triggering emergers, cold mornings keeping fish active through midday warming cycle
- Best Window: Late afternoon to dark for Drakes, midday 11am-2pm for PMDs, early mornings before wind builds mid-week
Generated weekly from live USGS gauge readings, weather forecasts, and recent fly shop reports. Updates Friday mornings.
About this Water
- Spring Creek
- Best months: June–Oct, peak late June–July (Green Drakes)
Henry's Fork of the Snake River below Island Park Reservoir is one of the most celebrated trout rivers in the world. The Last Chance section — a broad, flat spring creek meadow — hosts rainbow trout of legendary selectivity rising to Green Drake, PMD, and Trico hatches from June through September. The Box Canyon above Island Park offers a completely different experience: tumbling pocket water with large aggressive fish. Harriman Ranch State Park protects the finest stretch.
The Henry's Fork Green Drake hatch in late June is one of the great spectacles in fly fishing — vast carpets of drakes lifting off the Last Chance flat while enormous rainbows sip them with surgical precision.
January Outlook
The Ranch section of the Henry's Fork is closed to fishing until April 1. The lower Henry's Fork below Ashton is open year-round but fishing in January is slow — cold water and minimal hatch activity. The most dedicated anglers find midge activity on mild afternoons.
Productive Patterns
- Zebra Midge
- RS2
- Juju Baetis
- WD-40
Tips
Below Ashton on the lower Fork, midge fishing in the slow sections can produce fish on mild January afternoons. The Ranch is closed. The fall/winter tailout sections near the mouth hold fish.
Water Notes
Reservoir-regulated. Ranch closed until April 1. Lower Fork open but cold 36–44°F.
February Outlook
Ranch section still closed. Lower Henry's Fork midge activity continues. February brings slightly more activity than January as days lengthen. Still not a destination fishing month.
Productive Patterns
- Zebra Midge
- RS2
- Midge Larva
Tips
Fish the lower fork sections below Ashton for the most productive winter fishing. The Ranch opens April 1 — this is the planning month for the Green Drake hatch.
Water Notes
Lower Fork 36–44°F. Ranch closed. Minimal fishing activity.
March Outlook
The Ranch section opens April 1 — March sees pre-season anticipation building. The lower Henry's Fork can produce Baetis and midge activity in the second half of the month. One of the finest trout rivers in the world awakens in spring.
Productive Patterns
- Juju Baetis
- Zebra Midge
- RS2
- Soft Hackle
Tips
Lower Fork fishing improves significantly in March with BWO activity on warm afternoons. The Ranch opens in two weeks — plan your April trip. Fly shop reports from Last Chance are closely followed by anglers worldwide.
Water Notes
Lower Fork 42–50°F and improving. Ranch opens April 1. Spring arrives late at 6,000+ ft elevation.
April Outlook
The Railroad Ranch section opens April 1 to flies-only. Baetis and midges produce fish on good days. One of the world's most challenging and rewarding rivers.
Productive Patterns
- Baetis Sparkle Dun
- RS2
- CDC Midge
- Soft Hackle
Tips
The Ranch section requires stealth and precise presentations. Fish in the slick spring flows are incredibly selective. Long leaders, 6X tippet, and approach on your knees.
Water Notes
Regulated flows from Island Park Reservoir. 600–1,200 cfs in spring. Cold 42–50°F. Brilliant clarity.
May Outlook
PMD and Caddis hatches begin on the Henry's Fork. The ranch section produces difficult but rewarding dry fly fishing for large rainbows.
Productive Patterns
- PMD Sparkle Dun
- Elk Hair Caddis
- Pale Morning Dun
- RS2
Tips
The Henry's Fork is arguably the most technical dry fly river in North America. Fish rise to naturals of perfect size and presentation. A dry-fly-only mindset is rewarded here.
Water Notes
800–1,800 cfs. Clear cold water 48–56°F. Flows stable from the reservoir. The Ranch is walk-in only.
June Outlook
The famous Green Drake hatch arrives in late June — arguably the most anticipated hatch on any North American river. Large rainbows rise freely during the emergence.
Productive Patterns
- Green Drake Paradun
- Olive Comparadun
- CDC Green Drake
- Sparkle Dun
Tips
The Green Drake hatch typically occurs from late afternoon to dark. The Ranch section is the most reliable. Fish size 10–12 Green Drake patterns during the emergence window. Position and patience are everything.
Water Notes
1,200–3,000 cfs. Cold clear water 52–60°F. The Ranch section is prime. Stay on the right banks for access.
July Outlook
After the Green Drake, PMD and Caddis activity continues throughout July. Callibaetis hatches on the slower sections. The Lower Fork fishes hopper-dropper.
Productive Patterns
- Callibaetis
- PMD Cripple
- Hopper-Dropper
- Elk Hair Caddis
Tips
The lower Henry's Fork from Ashton to St. Anthony fishes differently — more hopper-friendly with easier wading and less technical demands. A good option when the Ranch is frustrating.
Water Notes
1,500–3,500 cfs. Water 58–65°F. Ranch section best in early morning before wind rises.
August Outlook
Hopper-dropper and Trico fishing on the lower sections. The Ranch section produces consistent Callibaetis activity in the mornings.
Productive Patterns
- Hopper
- Trico Spinner
- Callibaetis
- Elk Hair Caddis
Tips
The Ranch in August can be exceptional early morning before boat traffic and wind increase. The lower sections fish hopper-dropper all day.
Water Notes
1,200–2,500 cfs. Water 60–66°F. Wind typically picks up by 10am on the Ranch section.
September Outlook
Fall BWO season returns to the Henry's Fork. The Ranch section produces consistent hatches and the fish are exceptional. One of the finest September rivers in the West.
Productive Patterns
- Blue Winged Olive
- Mahogany Dun
- PMD Cripple
- Soft Hackle
Tips
The autumn BWO hatch on the Ranch section can be phenomenal — large fish rise freely to size 18–20 patterns. The section fishes best from mid-morning through afternoon on overcast days.
Water Notes
800–1,800 cfs. Cooling to 54–62°F. Clarity excellent. One of the world's great September experiences.
October Outlook
The Ranch section closes October 31. Excellent fall fishing through the month with BWO hatches and streamer action. The lower fork remains open through winter.
Productive Patterns
- Blue Winged Olive
- Streamer
- Mahogany Dun
- Nymph
Tips
October on the Ranch before the closure can produce the best fish of the year. Less pressure than September. Fish the morning rising windows carefully.
Water Notes
600–1,400 cfs. Cold 48–56°F. Low clear conditions. Ranch closes October 31.
November Outlook
The Ranch section closes October 31. The lower Henry's Fork below Ashton fishes through November with midge and Baetis activity. Cold conditions but fish are present. A quiet end-of-season month.
Productive Patterns
- Zebra Midge
- Juju Baetis
- RS2
- Midge Cluster
Tips
The lower Fork stays open year-round. November midge fishing is productive on mild days. The Ranch is closed through spring — enjoy the off-season solitude of the lower river.
Water Notes
Lower Fork 38–48°F. Ranch closed. Cold and quiet.
December Outlook
Winter on the Henry's Fork. The lower sections below Ashton fish on mild days for the most dedicated. The Ranch is closed and the Last Chance area is quiet. A world-class river at rest through its winter season.
Productive Patterns
- Zebra Midge
- RS2
- Mercury Midge
Tips
December lower Fork fishing is for the very local and dedicated. The ranch basin is cold and windswept in winter. Plan the April–October season from the warmth of home.
Water Notes
Lower Fork 34–42°F. Ranch closed until April 1. Off season.
Hatch Calendar
| Insect | Peak | Active | Size | Productive Patterns |
|---|---|---|---|---|
| Green Drake Drunella grandis |
Jun | Jun, Jul | #10–12 |
|
| Pale Morning Dun Ephemerella inermis |
Jul | Jun, Jul, Aug | #16–18 |
|
| Callibaetis Callibaetis spp. |
Jul, Aug | Jun, Jul, Aug, Sep | #14–16 |
|
| Blue Winged Olive Baetis tricaudatus |
Apr, Oct | Apr, May, Sep, Oct, Nov | #18–22 |
|
| Brown Drake Ephemera simulans |
Jun | Jun | #10–12 |
|
| Caddis Hydropsyche / Brachycentrus spp. |
Jun, Jul | May, Jun, Jul, Aug, Sep | #14–18 |
|
| Salmonfly Pteronarcys californica |
Jun | Jun | #4–6 |
|
| Trico Tricorythodes spp. |
Aug, Sep | Jul, Aug, Sep | #22–24 |
|
Access & Approach
Last Chance and Harriman Ranch, ID. The Harriman Ranch section (Idaho Dept. of Parks & Recreation) charges a day-use fee (~$7). Wading only on the Last Chance flat — no floating. Box Canyon is walk-in only from the canyon rim. Henry's Fork Anglers in Last Chance is the essential local resource.
Nearby Fly Shops
- Henry's Fork Anglers
- TroutHunt
- Madison River Outfitters
- Big Sky Anglers
- Blue Ribbon Flies
- The Tackle Shop
Regulations & License
Fishing in Idaho requires a current license. Always verify season dates, bag limits, and any special-regulation waters before you fish.
Idaho fishing regulations & license →
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About Current
Henry's Fork conditions on Current combine real-time flow data (USGS, WSC, CDEC, CEHQ), weather, tide predictions, hatch probabilities calibrated to this specific water, and recent fly shop reports from the area.
Henry's Fork is one of 245 hand-curated waters in Current. The app and web forecast also generate AI outlooks for any unlisted river, lake, or saltwater flat anywhere in the world — drop a pin or paste a name and Current produces a fresh seasonal outlook with weather, flow context, and recommended techniques.
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