7-day U.S. Geological Survey chart
Recent flow
Discharge
11 cfs7.88 cfs
Sep 4Sep 11
Latest reading: 8.19 cfs. Stable over about 6 hours. Chart covers Sep 4 through Sep 11; readings are provisional and may be revised.
All California reports
San Joaquin River
Photo: California High-Speed Rail Authority Opens in a new tab. · Public domain
Should I go fishing?
Yes — worth going.
Best option: Wading. Wading is in play only where your chosen access has clear footing, legal entry, and no forced crossings.
Fishing rating94
Rating updatedRiver local time:
Why this recommendation?
USGS shows 8 cfs. The flow has been stable over about 6 hours. USGS marks this reading provisional and may revise it. USGS records for this date (2011-2025, 15 readings) show a typical middle range of 8 cfs to 38 cfs. Flow is within the typical range for this date, so weather, temperature, and access become the next checks.
Available live dataHighHow much of the live flow, weather, and alert data came back.
Confidence in this recommendationHighCurrent flow, weather, alerts, and trip-critical signals support this decision.
Usually checks again about every 45 minutes
If you go
- Check first
- Use the Middle Fork San Joaquin gauge for upper Sierra flow context.
- Try
- Start with USFS alerts and road status, not fly selection.
- Leave when
- Skip the San Joaquin when Mammoth Pool access or launch closures cut off the reach you intended to use, when snowmelt is still pushing unsafe water, when smoke or fire restrictions turn forest travel into guesswork, or when you have not separated upper trout water from lower restoration-reach rules.
Flow and weather
Showing server-checked river conditions while current readings refresh.
- Flow
- 8.19 cfs
- Stable over about 6 hoursU.S. Geological Survey may revise this readingWater 56.5°F · 24h high 64.4°F · USGS provisional
- Air forecast
- 70°F
- Next 24h high
- 82.0°F
NWS air forecast near
- Rain chance
- 0%
Latest stored weather check
Clear
- Wind
- 10 mph
- Weather checked
More forecast and source details
Clear
National Weather Service
Upper San Joaquin forecast point
The National Weather Service forecast is temporarily unavailable.
Live data
Where these readings come from
Current U.S. Geological Survey gauge: Middle Fork San Joaquin River near Mammoth Lakes
Stable over about 6 hoursU.S. Geological Survey may revise this readingObserved
Water 56.5°F · provisional · 24h high 64.4°F provisionalWater observed · high observed
Flies for this time of year
Seasonal starting points, not a live hatch report. Match what you see on the water.
- Grasshopper PatternsHopperView fly guide ↗
- Beetle PatternsbeetleView fly guide ↗
- Ant PatternsantView fly guide ↗
- Caddis Patterns by Stagesmall caddisView fly guide ↗
- Zebra MidgeView fly guide ↗
See flies for every season
SeasonWhat to look forFlies to try
Late spring
What to look forStoneflies, caddis, early mayflies
Summer
What to look forCaddis, PMDs, yellow sallies, terrestrials
Late summerThis season
What to look forTerrestrials, small caddis, midges
FallThis season
What to look forBWOs, October caddis, midges
Flies to try
Each fly name opens its matching Fly Box guide.
More fishing tips
Methods, fish species and trip notes
How to fish San Joaquin River today.
A good San Joaquin trip is a section-by-section trip. If upper Sierra roads, flows, and forest alerts line up, fish pocket water, lake inlets, and cool smaller stream influence. If closures or runoff interfere, use a nearby Sierra alternative.
Snowmelt runoff
Expect cold, high, difficult water. Focus on safe edges or wait for flows to drop.
Stable summer flow
Fish pocket water, riffles, lake inlets, and shaded edges with dry-droppers or nymphs.
Low clear late season
Use smaller flies, longer leaders, and careful approaches.
Closure or fire restrictions
Move to another water instead of pushing into closed forest or unsafe smoke conditions.
Wading, bank fishing or floating?
Best access methodWading
These scores compare the risks of wading, bank fishing, and floating.
Wading · Best fit94/100
Wading is in play only where your chosen access has clear footing, legal entry, and no forced crossings.
Bank fishingNot recommended
This report does not recommend bank fishing on this reach.
FloatingNot recommended
This report does not recommend floating this reach.
Full river report
Is San Joaquin River worth the trip today? Check flow, weather, hatches, access, and rules for California before you go.
The San Joaquin is too broad for one generic report. This page anchors the fly-fishing plan on upper Sierra trout water near the Mammoth Pool and Middle Fork context, while noting that lower-river restoration reaches have different rules, access, and species concerns.
Fishing words used on this page
- U.S. Geological Survey (USGS) gauge
- A USGS gauge is an official river station that measures flow or water height.
- Cubic feet per second (cfs)
- Cubic feet per second, or cfs, shows how much water passes the gauge each second.
- Nymph
- A nymph is a young water insect. Anglers also use the word for a fly that copies it.
- Riffle
- A riffle is shallow, fast water broken by rocks.
- Blue-winged olive (BWO)
- Blue-winged olives, or BWOs, are small mayflies that often hatch in cool or cloudy weather.
- Caddis
- Caddis are small water insects. The adults look a little like tiny moths.
- Emerger
- An emerger copies an insect as it rises from below the water toward the surface.
- Midge
- Midges are tiny flies and a common trout food, especially in cold water.
- Pale morning dun (PMD)
- Pale morning duns, or PMDs, are light-colored mayflies that often hatch in warmer months.
- Pocket water
- Pocket water is a small calm spot among rocks or fast current.
Why this call
Why this score
FlowHelps
USGS shows 8 cfs. The flow has been stable over about 6 hours. USGS marks this reading provisional and may revise it. USGS records for this date (2011-2025, 15 readings) show a typical middle range of 8 cfs to 38 cfs. Flow is within the typical range for this date, so weather, temperature, and access become the next checks.
SeasonHelps
Fall: Cooler weather and lower water can improve trout fishing before storms close access.
Water temperatureHelps
USGS water temperature is about 56.5F, and the rolling 24-hour high did not trigger a heat caution. USGS marks the temperature data provisional and may revise it.
Public alertsHelps
No active NWS alert was returned for this forecast point.
Fishing usefulnessHelps
Skip the San Joaquin when Mammoth Pool access or launch closures cut off the reach you intended to use, when snowmelt is still pushing unsafe water, when smoke or fire restrictions turn forest travel into guesswork, or when you have not separated upper trout water from lower restoration-reach rules.
Trip notes
Check these before you choose a reach.
Use the Middle Fork trend as upper-river context and combine it with access alerts before you commit. Stable summer flows and cooler water are the best fit. Hard runoff, closure-driven detours, or fire-season disruptions should move you to another Sierra plan.
Skip the San Joaquin when Mammoth Pool access or launch closures cut off the reach you intended to use, when snowmelt is still pushing unsafe water, when smoke or fire restrictions turn forest travel into guesswork, or when you have not separated upper trout water from lower restoration-reach rules.
Choose the upper-river objective first: Mammoth Pool area access, Middle Fork context, or another specific Sierra area you can verify as open. Once that is clear, fish a smaller reach thoroughly instead of trying to solve the entire San Joaquin system in one trip.
If the San Joaquin is blocked by closures, runoff, or smoke, pivot to the Merced for another reach-aware Sierra freestone plan or to Owens if an Eastern Sierra option offers a cleaner access and temperature setup.
San Joaquin River access and rules.
Use these places as starting points. Open the access link below and check posted signs before you park or enter.
Before you go
Verify CDFW's current San Joaquin River rules for the exact reach you plan to fish. Upper Sierra trout water and lower restoration/anadromous reaches should not be treated as one rule set.
Where to access the river
Mammoth Pool Recreation Area
A key upper San Joaquin planning area, but access and launch work can change by season and alerts.
Middle Fork San Joaquin gauge context
Useful for flow planning near the upper Sierra trout system.
Sierra National Forest roads
Road, snow, fire, and project closures can decide the trip before fishing conditions do.
Lower San Joaquin restoration reaches
Important conservation context, but different from the upper trout plan.
- USFS alerts can affect roads, boat launches, campgrounds, and fire use.
- Spring runoff can make the river unsafe even when roads are open.
- Forest travel can involve long distances without services or cell coverage.
- Lower river restoration reaches have private land, access, and species issues that differ from the upper Sierra.
- Preserve URLs if a future page splits upper and lower San Joaquin reaches.
Sources and report details
Official agencies and primary river operators come first. Secondary tools are labeled so you know what carries the most weight.
Rules and closures
Check what is allowed, where the rule applies, and whether the river is open.
Flow and weather
Check the latest river reading and forecast before you leave.
Access and land
Check public entry points, land rules, and seasonal access changes.
More helpful links
Use these links for stocking, safety, and other local details.
See all 7 checked sources
Rules and closures
Check what is allowed, where the rule applies, and whether the river is open.
What this source covers
Open the current rules and check the river section, season, and special limits.
What this source covers
Open the current rules and check the river section, season, and special limits.
Flow and weather
Check the latest river reading and forecast before you leave.
What this source covers
Open this page and check the latest safety advice before your trip.
What this source covers
Open this river reading to check the latest level, flow, and update time.
Access and land
Check public entry points, land rules, and seasonal access changes.
What this source covers
Open the land or access page, then check signs before you park or enter.
What this source covers
Open the land or access page, then check signs before you park or enter.
More helpful links
Use these links for stocking, safety, and other local details.
What this source covers
Open this page for more river information and check when it was last updated.
How this report was checked
How this report was checked
Reviewed byBlueStreamFly River Review Team
Trip guidance checked
What was checked: This San Joaquin report is maintained from current Forest Service access alerts, California regulation, flow, weather, and restoration sources so anglers can plan the upper Sierra version of the river without blurring it into lower restoration water.
Live measurements and forecasts keep their provider timestamps. Rules, access, and trip guidance use the source-review date shown here. BlueStreamFly planning advice is editorial interpretation, not an agency notice.
First-hand experience: BlueStreamFly does not claim a first-hand visit or local field test for this report unless a real contributor is explicitly named and linked.
Quick questions
Which San Joaquin River section does this cover?
It focuses on upper Sierra trout planning near the Middle Fork and Mammoth Pool context, while flagging lower-river restoration issues.
What gauge should I check?
Use USGS 11224000, Middle Fork San Joaquin River near Mammoth Lakes, as upper Sierra flow context.
Is Mammoth Pool always accessible?
No. Check Sierra National Forest alerts, road conditions, fire restrictions, and seasonal closure information before going.
Can I use one rule summary for the whole river?
No. The river is long and section-by-section. Check CDFW for the exact reach.