Flathead River
Glacier National Park · Middle & South Forks
NW Montana, USA
Open live forecast →Target species: Cutthroat and Bull Trout.
Stream gauge: 12355500. Flow and water temperature update on every refresh.
Weekly AI Outlook as of 06/05/26
The Flathead is running 12,400 cfs with 48°F water — still big and cold but dropping fast from peak runoff. Salmonfly emergence is imminent once water temp hits 50-52°F, which could happen this week with forecast highs in the low 70s. No recent shop intel — outlook based on current conditions. Focus pre-hatch nymph patterns and streamers in deeper slots. Once the hatch triggers, it'll move upstream quickly through each fork.
- Flow: 12,400 cfs and dropping — still pushy water but fishable in back eddies and slower runs. Target protected lies behind boulders.
- Hatches: Salmonfly emergence just days away — 48°F water needs 2-4 more degrees. Golden stones and caddis active once bugs start moving.
- Water Temp: 48°F approaching critical 50-52°F Salmonfly threshold. Thursday's 72°F air could be the trigger for emergence to begin.
- Best Window: Midday warming crucial for bug activity. Fish 11am-4pm when air temps peak and stone nymphs become most active near bottom.
Generated weekly from live USGS gauge readings, weather forecasts, and recent fly shop reports. Updates Friday mornings.
About this Water
- Freestone
- Best months: June–Sept, peak July–Aug
The three forks of the Flathead River — North, Middle, and South — drain Glacier National Park and the Bob Marshall Wilderness, producing some of the cleanest, coldest water in the lower 48. The mainstream Flathead below the confluence at Hungry Horse offers classic Montana freestone fishing for native westslope cutthroat and bull trout (catch-and-release only on bulls). Float trips dominate. The forks themselves offer wilderness fishing for cutthroat in pocket water and gravel runs. Hatches are predictable: salmonflies and golden stones in late June, caddis and PMD through summer.
The Flathead drainage holds one of the last strongholds of native bull trout in the lower 48 — a federally threatened species protected by mandatory catch-and-release and strict identification requirements.
January Outlook
The Flathead River system is largely inaccessible in January. Heavy snowpack closes the North Fork road above Columbia Falls and the Middle Fork canyon is frozen along the banks. The main stem near Kalispell can provide occasional midging on mild days, but fishing is difficult and not worth the effort for most anglers.
Productive Patterns
- Zebra Midge
- Midge Larva
- RS2
Tips
If you're local and determined, the lower main stem near Kalispell can fish on mild afternoons. Better to wait for May. Snowshoe or ski access to park sections is available for winter wilderness experiences.
Water Notes
Main stem 600–1,500 cfs. Bank ice. North and Middle Fork roads may be impassable. Check road conditions before venturing out.
February Outlook
February is essentially off-season for the Flathead. Snow depth peaks and access to all three forks is limited. The lower main stem near Kalispell provides the only realistic open-water fishing — midge nymphing in slow, deep pools on the warmest days.
Productive Patterns
- Zebra Midge
- RS2
- Pheasant Tail Nymph
Tips
The main stem near the Highway 2 bridges is the only reliable winter access point. Focus on the deepest pools from 10am–2pm. The rest of the system is inaccessible and frozen.
Water Notes
Main stem 500–1,000 cfs. Cold and icy. North Fork road closed above Columbia Falls.
March Outlook
March sees the Flathead beginning to stir but remains largely locked in winter. Occasional midge hatches on the lower main stem on sunny days. Snowmelt begins by late March and flows start rising. Not a fishable month for most anglers.
Productive Patterns
- Zebra Midge
- Blue Winged Olive (small)
- RS2
Tips
Late March occasionally produces BWO hatches on warm afternoons on the lower main stem. The North Fork road often doesn't open until late April. Patience — May is the prize.
Water Notes
1,000–3,000 cfs and rising with early snowmelt. Lower main stem only. North Fork road typically closed.
April Outlook
April runoff begins in earnest. The main stem blows out by mid-April with glacial snowmelt. The North Fork road usually opens mid-to-late April allowing early access to the upper drainage. Not a typical fishing month but the North Fork just below the Canadian border can produce cutthroat on streamers between clarity windows.
Productive Patterns
- Streamer
- Stonefly Nymph
- Hare's Ear
Tips
Check the North Fork road opening date at Glacier National Park. When snow recedes, the upper forks provide the only clear water. Streamers work in off-color conditions.
Water Notes
Main Flathead 5,000–15,000+ cfs at peak runoff. North Fork above Polebridge may have fishable visibility windows in early April before peak runoff.
May Outlook
The Flathead River system drains Glacier National Park and one of the largest wilderness areas in the lower 48. May is runoff season — fish the Middle Fork sections nearest the mountain front for first fishable conditions.
Productive Patterns
- Streamer
- Stimulator
- Elk Hair Caddis
- Hare's Ear
Tips
The Middle Fork clears first above Hungry Horse. Wade-fish the braided sections near West Glacier before the main stem blows. Stonefly nymphs are the workhorse when visibility is limited.
Water Notes
Middle Fork 2,000–8,000+ cfs. North Fork 1,000–5,000 cfs. Main Flathead highly variable. Check gauges daily.
June Outlook
The Flathead's Salmonfly hatch is one of Montana's finest spectacles. Large stoneflies on all three forks as runoff subsides. A bucket-list early summer experience.
Productive Patterns
- Salmonfly #4
- Golden Stone
- Stimulator
- PMD
Tips
Call Whitefish or Columbia Falls fly shops for the Salmonfly hatch location — it moves quickly upstream through each fork. The North Fork above Columbia Falls is often accessible when the lower river is still high.
Water Notes
All three forks dropping from peak. Middle Fork prime at 1,500–3,500 cfs. North Fork 600–2,000 cfs. Best in late June.
July Outlook
Excellent float fishing on all three forks. Golden Stones, PMDs, and Caddis produce consistent dry fly action. The North Fork inside Glacier National Park is spectacular for backcountry float fishing.
Productive Patterns
- Golden Stone
- PMD Cripple
- Elk Hair Caddis
- Hopper (late July)
Tips
Float the North Fork from the Canadian border to Polebridge for a wilderness experience. The Middle Fork canyon above Hungry Horse is stunning. All-day dry fly fishing with large cutthroat trout.
Water Notes
Middle Fork 800–2,000 cfs. North Fork 400–1,200 cfs. Prime float conditions. Water 54–62°F.
August Outlook
Hopper season on all three forks. Native westslope cutthroat trout attack terrestrials aggressively in the gin-clear glacial water. One of Montana's finest August cutthroat rivers.
Productive Patterns
- Dave's Hopper
- Chubby Chernobyl
- Parachute Ant
- Elk Hair Caddis
Tips
The North Fork's westslope cutthroats eat hoppers with abandon. Glacier National Park regulations apply on sections within the park — check current rules. Float the lower North Fork for best hopper coverage.
Water Notes
Middle Fork 600–1,500 cfs. North Fork 300–900 cfs. Excellent conditions throughout.
September Outlook
Exceptional September fishing on all three forks. Cooling glacial waters, BWO hatches, and fish in prime condition. Bull trout become more active ahead of spawning.
Productive Patterns
- Blue Winged Olive
- Hopper
- Streamer
- Elk Hair Caddis
Tips
September on the North Fork inside Glacier is a mountain experience few anglers ever access. Float camp from the border to Columbia Falls for 3 days of unmatched wilderness fishing. Bull trout must be released unharmed.
Water Notes
Middle Fork 500–1,000 cfs. North Fork 250–700 cfs. Crystal clear glacier water 50–58°F.
October Outlook
Fall streamer fishing and bull trout spawning season. The Flathead system is one of the last strongholds for bull trout — treat them with reverence.
Productive Patterns
- Articulated Streamer
- Blue Winged Olive
- Sculpin
- Woolly Bugger
Tips
Large bull trout move up tributaries to spawn in October — observe but don't target spawning fish. The resident westslope cutthroats and rainbows remain active. Streamer fishing the deep main stem pools produces excellent results.
Water Notes
Middle Fork 400–800 cfs. North Fork 200–500 cfs. Cold 42–52°F. Fall colors spectacular.
November Outlook
Late season on the Flathead. Midge fishing in the main stem pools for committed anglers. The North Fork sections closest to Columbia Falls are most accessible.
Productive Patterns
- Zebra Midge
- RS2
- Soft Hackle
- Pheasant Tail
Tips
The Flathead in November is about solitude as much as fish. Fish the lower Middle Fork near its confluence. Cold and quiet — bring layers.
Water Notes
Main stem 800–2,000 cfs. Cold 36–44°F. Variable November flows. Access roads to North Fork may require 4WD.
December Outlook
The Flathead closes down for winter. Deep snow isolates the North Fork and Middle Fork canyon. The lower main stem near Kalispell is the only open-water fishing available — midging in slow, deep pools for locals only. Not a worthwhile destination month.
Productive Patterns
- Zebra Midge
- RS2
- Midge Pupa
Tips
December fishing on the Flathead is for local diehard midge fishers only. Main stem pullouts near Kalispell. The North Fork road closes completely. Spend December planning the float trip you'll take in July.
Water Notes
Main stem 500–1,000 cfs. Bank ice forming. North Fork and Middle Fork canyon inaccessible. 4WD required for any river access.
Hatch Calendar
| Insect | Peak | Active | Size | Productive Patterns |
|---|---|---|---|---|
| Salmonfly Pteronarcys californica |
Jun | Jun, Jul | #4–8 |
|
| Golden Stonefly Hesperoperla pacifica |
Jul | Jun, Jul, Aug | #8–12 |
|
| Caddis Hydropsyche / Brachycentrus spp. |
Jul, Aug | Jun, Jul, Aug, Sep | #14–18 |
|
| Pale Morning Dun Ephemerella inermis |
Jul | Jul, Aug | #16–18 |
|
| Hoppers Acrididae / Tettigoniidae |
Aug | Jul, Aug, Sep | #8–12 |
|
Access & Approach
Kalispell and Whitefish are the main bases. Glacier National Park boundary affects access on the North and Middle forks. Montana fishing license required; bull trout are catch-and-release only and require specific identification skills. Some forks require multi-day raft trips.
Nearby Fly Shops
- Wild Montana Anglers
- Bigfork 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
Flathead 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.
Flathead River 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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