Freestone · Mixed · Montana, US

Dearborn River

A rocky, fast-flowing stretch of the Dearborn River winding between pine-covered canyon walls in Montana.

The Dearborn is a flashy little freestone off the Rocky Mountain Front that empties into the Missouri near Craig.

Tomorrow · About as good as it gets
Pheasant Tail
Forecast · Tomorrow
About as good as it gets
On the feed top to bottom — start on the rises with a dry, drop a nymph if they stay down.
75% projected
Today's fly
Pheasant Tail
Pheasant Tail
Conditions on the water · Tomorrow
Live gauge
Level
Steady
0.93 m
Water temp11.1°C
ClarityClear
Weather13°C
WindN 10 km/h
Pressure1007 hPa
Rain · recent0.0 mm
Rain · ahead0.0 mm

The nearest gauge doesn't record temperatures, so we've estimated it — defer to the river keeper's advice.

Water temperature for Brown Trout
Ideal
11°C est.ideal 10–16°C
0°14°28°
How to fish it · for Brown Trout
When
Nymphing can work through most of the day.
Where
Cover mixed depths.
Method
Start with tight-line nymphs and adjust if fish rise or drift higher.
Kit
9 ft #4 rod, floating line, 12 ft tapered leader to 4–5 lb fluoro tippet.
Why this works
Excellent — water temperature is right today, though time of day could be better.
Likely species
Mayflies
terrestrials
Hatch timeline · tomorrowPeak at 12pm

12pm(now) — Mahogany Dun

Stage: On emergersApproach: Emerger or dryActivity: 95%
Also:Reed Smut37%
Peak emergence windowDegree-days at peak8 food groups active

Peak activity at 12pm — Mahogany Dun (Mahogany Dun, Peak emergence window)

Sub-surface · on the nymphunder the surface

Hatch predictions

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Beyond the hatch · worth watchingambient prey(1)

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Evidence
Records-basedModerate confidence

Based on species-occurrence records, not local invertebrate surveys.

Through the year
0–3 scale · September highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
2
1
1
2
2
2
2
2
2
2
Brown DunHatch
2
3
3
3
3
3
3
2
Western Green DrakeHatch
2
2
Flav (Small Western Green Drake)Hatch
2
3
2
Mahogany DunHatch
2
2

Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.

Ranked for today
Brown Trout fly box
SD
Sex Dungeon
2-6 · Pattern
Proven pattern for this period
Permits & access
Permit required — see local rules.
  • Montana licence
  • Short flow window — fish it early, leave it alone once it draws down
  • Yellowstone/westslope cutthroat are native here — handle and release them gently.
What's coming
Plan ahead
5-day outlook
Other water nearby · 3
Missouri River
18 km
Rainbow trout · Brown trout
Sun River
47 km
81
Brown trout · Rainbow trout
Smith River
56 km
82
Brown trout · Rainbow trout
Gallery · 2
  1. A rocky, fast-flowing stretch of the Dearborn River winding between pine-covered canyon walls in Montana.
    The Dearborn River
  2. Terrain map of the venue
    Terrain map
About this water

The Dearborn is a flashy little freestone off the Rocky Mountain Front that empties into the Missouri near Craig. It comes up fast and drops fast, which gives it a short, sweet window in early summer when the canyon stretch can be floated and the cutthroat and rainbows come up willingly for a dry. Miss the window and it's a bony trickle by August. People floating the famous Missouri tailwater nearby often forget it's even there, which is exactly its charm.

  • Mixed
Water quality · US Clean Water Act
  • Aquatic life: Impaired
What this classification means

EPA ATTAINS assessment unit 'Dearborn River' (MT41Q003_010), 2021 Integrated Report. Aquatic Life use: Not Supporting. Listed impairment causes: Temperature. This is a Clean Water Act assessment-unit classification (the US analogue of WFD), not a live reading.

Status is for the Clean Water Act assessment unit covering this reach.

EPA ATTAINS (Clean Water Act) · MT41Q003_010

The full read · show the working · for Brown Trout · confidence 90%
How the 83 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time55 × 13%7.2
Pressure80 × 7%5.6
Insect activity60 × 12%7.2
Conditions total= 83
Can you trust it?
Water temperaturelive gauge readinggauge
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout Third Saturday of May → Last day of February
Related guides
Euro Nymphingsubsurface methods
Booking & contacts