Southwest Montana, Montana
Big Hole River Fishing Report: May 18, 2026
Big Hole River is fishable but mixed today.
- Status
- fair
- Flow trend
- falling
- Best window
- Late morning through evening as clarity allows
- Best methods
- nymphs, streamers, dry flies
Quick Summary
Big Hole River is fishable but mixed today. USGS showed 2,800 cfs and 3.66 feet at 7:15 AM, with the flow trend falling. Water temperature was 45 F. Start with nymphs, then watch for late-day mayfly, caddis, or midge activity where the water settles.
Conditions Snapshot
| Field | Value |
|---|---|
| Status | Fair |
| Flow | 2,800 cfs at 7:15 AM |
| Gauge Height | 3.66 feet |
| Water Temp | 45 F |
| Clarity | Not reported |
| Trend | Falling |
| Best Window | Late morning through evening as clarity allows |
| Best Method | nymphs; streamers; dry flies |
| Wadeability | Limited |
Weather
For Melrose, MT, the National Weather Service forecast says: Today: Mostly sunny, with a high near 49. North wind 9 to 20 mph, with gusts as high as 29 mph. Plan around wind, changing light, and any showers or storms rather than assuming a full-day dry fly window.
River Notes
The best starting point is water that matches the current gauge: inside seams, protected banks, riffle drop-offs, and slower buckets rather than the heaviest current. A falling trend is worth watching through the day; if the hydrograph turns sharply upward, clarity and wade safety can change before hatch timing does. Missing field values are left as Not reported rather than filled from guesswork.
Hatch Activity
Current hatch guidance is based on seasonal May patterns for this river system, recent public report context where available, and today’s official gauge/weather check.
| Hatch | Size | Notes |
|---|---|---|
| Blue Winged Olive | 18-22 | Cloudy periods |
| Caddis | 14-18 | Carry pupa and adults |
| March Brown | 10-12 | Sporadic larger mayfly |
| Skwala/stonefly nymph | 8-12 | Searching nymph in heavier water |
Recommended Flies
| Category | Fly | Size | Notes |
|---|---|---|---|
| Dry | Blue Winged Olive Comparadun | 18-22 | Use over steady risers |
| Dry | BWO Sparkle Dun | 18-22 | Match small olives in softer seams |
| Nymph | Pheasant Tail | 14-18 | Mayfly nymph before hatches |
| Nymph | Caddis Pupa | 14-18 | Swing or dead drift before activity |
| Streamer | Olive Sculpin | 4-8 | Use on banks if water has color or light is low |
Tactics
Start with nymphs in defined lanes and adjust weight or leader length before changing flies. If fish begin rising, simplify to a single dry or dry with an emerger/dropper and lengthen the leader. In bright or windy periods, return to subsurface presentations along protected banks and broken water. Re-check the gauge before wading new crossings, especially if the trend changes from stable or falling to rising.
Gauge Links
| Gauge | Flow | Temp | Link |
|---|---|---|---|
| Big Hole River near Melrose MT | 2,800 cfs | 45 F | USGS 06025500 |
Sources
Official sources checked: USGS station 06025500 and the National Weather Service forecast for the Melrose, MT area. This report is an original Custom FlyBox summary based on current official gauge and weather data, with local public conditions reports reviewed separately for hatch, access, and method context.