Freestone · Mixed · Colorado, US

Boulder Creek (Boulder Canyon)

Boulder Creek flowing swiftly through a rocky canyon lined with pine trees and granite boulders in Boulder Canyon, Colorado.

Boulder Creek up in Boulder Canyon is the quintessential Front Range small-water quick-hit — a tumbling little freestone right beside CO-119 that holds eager browns and rainbows and asks nothing more than a short cast and a willingness to scramble.

Tomorrow · Not the day for it
Sex Dungeon
Forecast · Tomorrow
Not the day for it
Not much stacked in your favour today. Worth an hour if you are nearby, not worth the special trip.
45% projected
Today's fly
SD
Sex Dungeon
Conditions on the water · Tomorrow
Live gauge
Level
Rising
1.43 m
Lifting fast
Water temp14.6°C
ClarityUnfishable
Weather20°C
WindN 13 km/h
Pressure1012 hPa
Rain · recent0.3 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 Rainbow Trout
Ideal
15°C est.ideal 10–18°C
0°14°28°
How to fish it · for Rainbow 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 insect activity could be better.
Likely species
Mayflies
Caddisflies
Hatch timeline · tomorrowPeak at 11am

12pm(now) — Reed Smut

Stage: On emergersApproach: Emerger or dryActivity: 40%
Also:Mahogany Dun24%Flying Ants23%
Peak emergence window5 food groups active

Peak activity at 11am — Reed Smut (Reed Smut, Peak emergence window)

Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 2 guilds with Pro.

Start free trial

14-day free trial. Cancel anytime.

Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Top prey shown — see all 4 with Pro.

Start free trial

14-day free trial. Cancel anytime.

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
1
2
2
2
2
2
2
2
2
2
2
1
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
Rainbow Trout fly box
SD
Sex Dungeon
2-6 · Pattern
Proven pattern for this period
Permits & access
Permit required — see local rules.
  • Colorado licence
  • Wild Trout special-regulation section in Boulder Canyon — verify CPW rules.
What's coming
Plan ahead
5-day outlook
Other water nearby · 3
St. Vrain Creek (Lyons)
25 km
20
Brown trout · Rainbow trout
Clear Creek (Golden)
29 km
Brown trout · Rainbow trout
Big Thompson River (canyon, below Lake Estes)
46 km
Brown trout · Rainbow trout
Gallery · 2
  1. Boulder Creek flowing swiftly through a rocky canyon lined with pine trees and granite boulders in Boulder Canyon, Colorado.
    Boulder Creek, Boulder Canyon
  2. Terrain map of the venue
    Terrain map
About this water

Boulder Creek up in Boulder Canyon is the quintessential Front Range small-water quick-hit — a tumbling little freestone right beside CO-119 that holds eager browns and rainbows and asks nothing more than a short cast and a willingness to scramble. It's small enough to wade in tennis shoes and flashy enough to muddy up after a storm, with a Wild Trout section in the canyon for those who want to keep it honest. Nobody's driving across the state for it, but for an after-work hour out of Boulder it's hard to beat, and the upper canyon thins the crowd nicely.

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

EPA ATTAINS assessment unit 'Boulder Creek, mainstem and tributaries.' (COSPBO02b_G), 2024 Integrated Report. Aquatic Life use: Not Supporting. Listed impairment causes: Metals Other Than Mercury. 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) · COSPBO02b_G

The full read · show the working · for Rainbow Trout · confidence 90%
How the 84 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time80 × 13%10.4
Pressure75 × 7%5.3
Insect activity62 × 12%7.4
Conditions total= 84
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout 1 January → 31 December
Related guides
Euro Nymphingsubsurface methods
Booking & contacts