Big Wood - Little Wood Rivers Idaho Hatch Chart
South-central Idaho, near Sun Valley and Ketchum. The Big Wood and Little Wood Rivers share the same drainage basin in the Wood River Valley, flowing south through sagebrush and mountain terrain before joining near Carey. Both rivers hold wild rainbow and brown trout and share the same core hatch calendar - but they fish differently enough to be worth understanding separately.
The two rivers
Big Wood River
The primary fishery in the valley. The Big Wood runs from its headwaters above Ketchum south through the resort corridor, then into a more remote canyon below Bellevue before reaching the valley floor. The upper river near Ketchum and Hailey is well-accessed and heavily fished. The canyon section between Bellevue and Carey is less pressured and holds the best salmonfly and golden stone activity on the system. Wild rainbows throughout; brown trout more common in the lower reaches. Check current Idaho Fish and Game regulations - specific sections have catch-and-release rules and seasonal restrictions.
Little Wood River
A smaller, more intimate river draining the hills east of the Big Wood. Less access and less pressure than its larger neighbor. Wild rainbows in the upper water; browns in the lower river near the reservoir. The Little Wood warms more quickly than the Big Wood in summer - by August, fish in the lower reaches can be stressed by warm water. Focus on the upper river and early morning fishing in midsummer. The same regulations apply - confirm before you go.
Shop by type: dry flies, nymphs, Euro nymphs, hoppers and terrestrials, streamers.
Year at a glance
| Month | Primary hatches | Also carry | Typical sizes |
|---|---|---|---|
| Jan | Midges | BWO on mild days | 18-22 |
| Feb | Midges, BWO | Small stonefly nymphs | 16-22 |
| Mar | BWO, midges | Early Skwala on Big Wood | 14-22, Skwala 8-12 |
| Apr | BWO, Skwala, March Brown | Early caddis, runoff begins | 12-18 |
| May | Caddis, stonefly nymphs | BWO, high runoff typical | Caddis 14-16, stones 6-10 |
| Jun | Salmonfly, golden stone, caddis | PMD late month | Stones 4-10, caddis 14-16 |
| Jul | PMD, caddis, yellow sally | Hoppers start, golden stone fading | 14-18 |
| Aug | Hoppers, ants, caddis | Late PMD, beetles - upper river focus | Hopper 8-12, ant 14-16 |
| Sep | Hoppers, BWO, October caddis | Mahogany dun, streamers | 10-18, BWO 18-20 |
| Oct | October caddis, BWO | Midges, streamers for browns | Caddis 8-12, BWO 18-22 |
| Nov | BWO, midges | Small streamers | 18-22 |
| Dec | Midges | Small nymphs | 18-22 |
January
Both rivers fish year-round. Midge activity can produce surface action on calm, mild afternoons. The Big Wood near Ketchum is the most accessible option in winter. Fish hold in deeper slots and slow tailouts.
- Midges - 18-22. Red zebra midge or small Euro nymph in a two-fly rig through slow tailouts.
- Small dark stonefly nymphs along the bottom.
February
Same midge program with increasing BWO activity on overcast afternoons. The Big Wood valley can be cold in February - midday is the fishing window.
- Midges and BWO on gray days.
- Pheasant tail nymphs subsurface for Baetis.
March
Olives pick up. Skwala stoneflies begin on the Big Wood canyon section when water temperatures climb out of the low 40s - one of the earlier Skwala rivers in Idaho. The Little Wood tends to run colder longer and sees lighter Skwala activity.
- BWO - 16-20. Parachute BWO and Barr's Baetis emerger.
- Skwala - 8-12. Rubber-leg nymph along banks, Stimulator-style dry on warm afternoons on the Big Wood canyon. See nymphs and dry flies.
April
Olives and March Browns provide dry-fly opportunities on gray days. Caddis begin late in the month. Snowmelt runoff typically starts building toward the end of April - fish while you can before flows push.
- BWO and March Brown, 12-18, on cloudy afternoons.
- Skwala still works on the first warm bank water on the Big Wood.
- Early dark caddis.
May
Caddis can be excellent in early May on both rivers. Stonefly nymphs are migrating. Both rivers typically blow out mid-month with snowmelt - the Big Wood canyon clears faster than the upper river near Ketchum. Check stream gauges before making the trip.
- Caddis - 14-16. Elk hair caddis and the caddis assortment early in the month.
- Stonefly nymphs 6-10 from nymphs.
- BWO on gray afternoons when flows allow.
June
The signature month on the Big Wood. As flows drop and clear - typically mid-to-late June - the salmonfly hatch moves through the canyon section between Bellevue and Carey. This is the best salmonfly water on the system and receives far less pressure than better-known Idaho rivers. Golden stones follow and extend the big-bug window. The Little Wood sees golden stone activity but lighter salmonfly numbers.
- Salmonfly - 4-8. A West Fork Salmonfly against undercut banks and woody debris. Fish the leading edge of the hatch.
- Golden stone - 6-10. Overlaps and follows the salmonfly on both rivers.
- Caddis - 14-16 evenings. Elk hair.
- Late June: first PMD in riffles, 16-18. Pale Morning Dun.
July
Classic summer dry-fly fishing on both rivers. PMDs in the morning, caddis in the evening, yellow sallies in fast riffles. The upper Big Wood near Ketchum fishes well in July with good access and willing fish. The Little Wood is best fished early morning - it warms more quickly than the Big Wood by midday.
- PMD - 16-18. Pale Morning Dun with a pheasant tail dropper.
- Yellow sally - 14-16 in fast pocket water and riffles.
- Early hoppers along grass and sage banks - hoppers and terrestrials.
- Caddis evenings. Elk hair.
August
Hopper season on the Big Wood. Focus on the upper river and canyon section - water temperatures are cooler and fish are more active. On the Little Wood, restrict fishing to early morning and focus on the upper, higher-elevation water. The lower Little Wood can reach stressful temperatures for trout in August - if fish are sluggish or lethargic, move on and let them rest.
- Hoppers, ants, beetles - hoppers and terrestrials. A hopper-dropper with a small nymph underneath covers both feeding lanes.
- Evening caddis. Elk hair.
- Late PMD on cool mornings in the canyon and upper reaches.
September
One of the best months on both rivers. Crowds thin after Labor Day. Terrestrials hold through mid-month. Olives and October caddis return. Brown trout begin feeding aggressively ahead of the spawn on the lower Big Wood - streamer fishing picks up in the deeper runs. The Little Wood is fully fishable again as temperatures drop.
- Hoppers and ants until the first hard frost.
- BWO - parachute BWO and Baetis emerger, 18-20.
- Early October caddis - large orange dry, 8-12.
- Mahogany dun - 14-16 on overcast afternoons.
- Streamers in deeper slots at last light for pre-spawn browns.
October
Fall colors in the valley. October caddis and olives for willing fish. Brown trout in the lower Big Wood are staging - handle carefully and avoid disturbing fish on redds. One of the less-crowded and most scenic months on both rivers.
- October caddis and BWO.
- Midges in slow pools and tailouts.
- Streamers for brown trout in deeper runs on the lower Big Wood.
November
Short days, cold mornings. BWO and midges on the warmest part of the afternoon. The upper Big Wood near Ketchum is the most accessible and reliable option in late fall.
December
Midge and nymph program. The valley can be cold and snowy - the Big Wood near town is the practical option for winter fishing.
- Red zebra midge and small nymphs.
- Olive or black streamers in deeper slots.
A western dry and nymph assortment covers the core season on both rivers. Add a salmonfly pattern, hoppers, October caddis, and a streamer box for the full Wood River Valley experience.