Freestone · Volcanic · Eastern Sierra

Upper San Joaquin River

Upper San Joaquin River terrain map

The Upper San Joaquin is high-country freestone fishing at its purest — the Middle Fork rising in the wilderness around Thousand Island Lake and running down past Devils Postpile and Reds Meadow in a granite-and-pine canyon below Mammoth.

Marginal · Rainbow Trout
Parachute Adams · 12-18
Marginallive now
Slow going — pick your moments
River steady at a fishable height. Slow going — pick your moments and do not force it.
80% confidence
What moved it
  • Level1.06 mLast reading 23h ago
  • Water temp18.4°C
  • ClarityClear
Today's fly
Parachute Adams
Parachute Adams12-18
High-confidence seasonal pick
Conditions on the water
Live gauge
Level
Steady
1.06 m
Last reading 23h ago
Water temp18.4°C
ClarityClear
Weather19°C
WindSW 15 km/h
Pressure1018 hPa
Rain · recent0.0 mm
Rain · ahead1.2 mm

Live readings only. Trends shown where the gauge supports them.

Water temperature for Rainbow Trout
Warm — slow
18.4°Cideal 1018°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
Water at 18.4°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Hatch timeline · todayQuiet day

Hatch predictions

Today's headline hatch shown — see all 3 active hatches hour by hour with Pro.

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Sub-surface · on the nymphunder the surface

Hatch predictions

See the full sub-surface read with Pro.

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Beyond the hatch · worth watchingambient prey

Hatch predictions

Top prey shown — see all 2 with Pro.

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Evidence
ModelledModerate confidence

Modelled from regional ecology — no survey or occurrence data for this water yet.

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

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

Ranked for today
Rainbow Trout fly box
Permits & access
Permit required — see local rules.
  • General-season trout water (~late April–mid-November) but really gated by snowmelt and Reds Meadow road access
  • Verify CDFW rules and wilderness / Devils Postpile National Monument access
  • High-altitude, short season.
What's coming
Plan ahead
5-day outlook
Cooler water nearby · 1
Water here at 18.4°C — the fishing's alive, but these are cooler if you'd rather rest the warm water.
About this water

The Upper San Joaquin is high-country freestone fishing at its purest — the Middle Fork rising in the wilderness around Thousand Island Lake and running down past Devils Postpile and Reds Meadow in a granite-and-pine canyon below Mammoth. The trout are wild rainbows and browns, willing and unsophisticated the way fish that don't see much pressure tend to be, and the fishing is a backcountry pleasure: attractors and dry-droppers in the pocket water, a day spent as much for the place as the catch. It's snowmelt all the way, so the calendar is the snowpack's: roaring and unfishable through the peak melt, then dropping into prime shape through summer and into a quiet, golden autumn. Altitude is the other half of the story — it's cold up here, the season is short, and the road into Reds Meadow only opens when the snow lets it. Time it for the drop after runoff, hike in, and fish a river that still feels like wilderness.

  • Volcanic
Water quality · US Clean Water Act
  • Aquatic lifeSupporting
What this classification means

EPA ATTAINS assessment unit 'Middle Fork San Joaquin River (Madera County)' (CAR5406002020190822044334), 2024 Integrated Report. Aquatic Life use: Fully Supporting. 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) · CAR5406002020190822044334

The full read · show the working · for Rainbow Trout · confidence 80%
How the 38 is built — score × weight = contribution
Temperature87 × 28%24.4
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time40 × 13%5.2
Pressure75 × 7%5.3
Insect activity64 × 12%7.7
Conditions total= 76
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
Seasons & zones
  • TroutLast Saturday in April15 November
Related guides
Booking & contacts