Boulder River
Natural Bridge Canyon · McLeod to Big Timber
S Montana, USA
Open live forecast →Target species: Brown and Rainbow.
Stream gauge: 06200000. Flow and water temperature update on every refresh.
About this Water
- Freestone
- Best months: June–Sept, peak July–Aug
The Boulder River cascades from the Beartooth Plateau through a stunning limestone canyon to meet the Yellowstone near Big Timber. Its aquarium-clear water holds dense populations of wild rainbow and brown trout in a setting that rewards stealth and precision. The Natural Bridge Falls section is a spectacular landmark. The Boulder is one of Montana's better-kept secrets — less famous than its Yellowstone-area neighbors but no less productive.
The Boulder's water clarity is so exceptional that anglers can sight individual fish in pools 4-5 feet deep — a rare and exciting characteristic that rewards stalking skills over blind fishing.
January Outlook
The Boulder River is locked in winter. The McLeod area road is open but the canyon above Natural Bridge is inaccessible in deep snow. Midge fishing in the lower reaches near McLeod is possible on mild days but not worth a special trip.
Productive Patterns
- Zebra Midge
- RS2
Tips
The Boulder in January is best left alone. The lower section near McLeod can produce midging on the warmest days but the effort-to-reward ratio is poor. Wait for June.
Water Notes
200–500 cfs. Mostly frozen. Water 32–38°F. Very limited fishing potential.
February Outlook
February remains firmly off-season. The canyon is inaccessible and the lower river is cold and slow. The Boulder's season opens dramatically in June with Salmonfly and Golden Stone hatches.
Productive Patterns
- Zebra Midge
- RS2
Tips
The Boulder is a summer and fall river. February is for planning the June Salmonfly season. Call Billings fly shops in May for current hatch timing.
Water Notes
200–450 cfs. Cold — 32–38°F. Canyon largely inaccessible. Off season.
March Outlook
March sees the Boulder beginning to wake up. Occasional midge activity in the lower section. Snowmelt builds flows toward the June peak. Not a fishing destination in March but the first signs of spring activity are emerging.
Productive Patterns
- Zebra Midge
- Pheasant Tail
- RS2
Tips
Late March can produce brief midge and early BWO activity on warm afternoons in the lower canyon near McLeod. The river will peak in late May-June before the season opens in earnest.
Water Notes
300–800 cfs and rising. Water 38–48°F. Canyon road typically open. Not prime fishing.
April Outlook
April runoff arrives on the Boulder. The river typically blows out by mid-April with Beartooth snowmelt. The canyon above Natural Bridge is spectacular but largely unfishable in high, colored water.
Productive Patterns
- Streamer
- Stonefly Nymph (large)
Tips
April can provide streamer fishing in the lower sections when visibility allows. The Natural Bridge area floods dramatically in peak runoff. Monitor the gauge — the river changes rapidly.
Water Notes
500–2,500+ cfs. Turbid with Beartooth runoff. Very high flows in some years. Season typically begins when flows drop below 500 cfs in late May-June.
May Outlook
The Boulder is typically in full runoff through most of May. The river is high and off-color as the Beartooth snowpack melts. The Salmonfly hatch approaches as flows begin dropping in late May.
Productive Patterns
- Large Streamer
- Stonefly Nymph
- Rubber Leg Nymph
Tips
Watch the gauge daily in late May — when the Boulder drops below 500 cfs and begins clearing, the Salmonfly hatch is imminent. Call Billings or Big Timber fly shops for the exact timing.
Water Notes
1,000–3,000 cfs dropping toward June levels. Late May can produce the first clear-water fishing of the season.
June Outlook
The Boulder runs high and cold from the Beartooth front in June. Salmonfly and Golden Stonefly hatches arrive when flows moderate. Early summer fishing is excellent in the pocketwater.
Productive Patterns
- Salmonfly (large)
- Golden Stone
- Streamer
- Rubber Leg Nymph
Tips
The Natural Bridge section above McLeod is spectacular when flows drop to fishable levels. Pocketwater fishing with attractor patterns is productive. Watch the gauge daily — this river changes fast.
Water Notes
1,000–3,000 cfs early June dropping to 500–1,000 by month end. Crystal clear water with Beartooth runoff character.
July Outlook
Prime summer fishing. The Boulder's aquarium-clear water and abundant rainbows and browns make this a spectacular small-river experience.
Productive Patterns
- Stimulator
- Elk Hair Caddis
- PMD Parachute
- Hopper (late July)
Tips
The Boulder's clarity demands stealth — approach from downstream and keep a low profile. The fish in this river are wild and responsive to precise presentations. Wade wet in July.
Water Notes
300–700 cfs. Clear as gin. Water 58–65°F. Outstanding visibility for sight fishing.
August Outlook
Hopper season on a spectacular small river. The canyon sections hold surprising numbers of large fish.
Productive Patterns
- Dave's Hopper
- Chubby Chernobyl
- Elk Hair Caddis
- Parachute Adams
Tips
The Natural Bridge Falls is worth the visit even without fishing. The canyon above McLeod is narrow with dense streamside vegetation — roll casts required. Fish are not heavily pressured.
Water Notes
200–400 cfs. Low and clear. Warm afternoons — fish mornings. Water 62–68°F.
September Outlook
Fall BWO hatches and pre-spawn browns. The Boulder is exceptional in September with cooling water and colored canyon walls.
Productive Patterns
- Blue Winged Olive
- Hopper
- Streamer
- Elk Hair Caddis
Tips
September is the most productive month on the Boulder for large fish. Browns come out of hiding for BWO hatches. Streamer fishing in the deep pools becomes effective.
Water Notes
150–350 cfs. Crystal clear. Water 50–60°F. Prime fall conditions.
October Outlook
The Boulder in October is excellent and uncrowded. Brown trout are pre-spawn and aggressive. BWO hatches on overcast afternoons. The Natural Bridge area has spectacular fall color.
Productive Patterns
- Articulated Streamer
- Blue Winged Olive
- Egg
- Soft Hackle
Tips
October is one of the best months for large fish on the Boulder. Pre-spawn browns attack streamers along undercut banks. Very little fishing pressure — the river is essentially private. Respect visible spawning redds.
Water Notes
150–350 cfs. Very low and clear. Water 42–52°F. Approach carefully — fish are easily spooked.
November Outlook
November wraps up the Boulder season. Cold temperatures and early snow can make the canyon difficult. Brown trout spawn concludes. Midge fishing in the lower section on mild afternoons.
Productive Patterns
- Zebra Midge
- RS2
- Pheasant Tail
- Juju Baetis
Tips
Lower canyon near McLeod can produce midge fishing on mild November days. The season is essentially over — most anglers leave the Boulder to its winter rest after October.
Water Notes
150–300 cfs. Cold 36–44°F. Canyon road typically open. Snow possible any day.
December Outlook
The Boulder River is closed for winter. The canyon sees deep snow and the river is locked in cold conditions. A season well-rested for the spectacular June opening ahead.
Productive Patterns
- Closed — winter season
Tips
The Boulder is best left alone in December. Plan the Salmonfly hatch season — it runs from late May through mid-June and is one of Montana's most dramatic fishing events.
Water Notes
100–250 cfs. Frozen in sections. Canyon road may require 4WD. Off season.
Hatch Calendar
| Insect | Peak | Active | Size | Productive Patterns |
|---|---|---|---|---|
| Blue Winged Olive Baetis tricaudatus |
Apr, Oct | Mar, Apr, May, Sep, Oct | #18–22 |
|
| Salmonfly Pteronarcys californica |
Jun | Jun, Jul | #4–8 |
|
| Golden Stonefly Hesperoperla pacifica |
Jul | Jun, Jul | #8–12 |
|
| Caddis Hydropsyche / Brachycentrus spp. |
Jul, Aug | Jun, Jul, Aug, Sep | #14–18 |
|
| Hoppers Acrididae / Tettigoniidae |
Aug | Jul, Aug, Sep | #8–12 |
|
Access & Approach
McLeod and Natural Bridge State Monument north of Big Timber. Multiple pullouts along Boulder River Road. No fees on public land. Walk-wade throughout — no float fishing in the narrow upper canyon.
Nearby Fly Shops
- Fly Fish Montana
- Dan Bailey's
- Yellowstone Angler
- Sweetwater Fly Shop
- Big Sky Anglers
Regulations & License
Fishing in Montana requires a current license. Always verify season dates, bag limits, and any special-regulation waters before you fish.
Montana fishing regulations & license →
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About Current
Boulder River 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.
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