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Generated mountain freestone river scene representing Montana's Boulder River, not an exact location photo
All Montana reports

Boulder River

Generated artwork: BlueStreamFly · Regional illustration; not the exact location.

Should I go fishing?

Check the water temperature first.

Water temperature is unconfirmed. Use a stream thermometer; stop trout fishing at 70°F or warmer, or sooner if fish show stress.

Rating updatedRiver local time:

Why this recommendation?

USGS shows 76 cfs. The flow has been stable over about 6 hours. USGS marks this reading provisional and may revise it. USGS records for this date (1948-2024, 76 readings) show a median near 134 cfs and the lower quartile near 80 cfs; today's flow is below normal for the date. This is below normal, so edge depth, temperature, and pressure matter.

Available live dataHighHow much of the live flow, weather, and alert data came back.
Confidence in this recommendationMediumWater temperature not verified; do not use this score to clear warm-water risk.
Usually checks again about every 45 minutes

If you go

Check first
RiverReports is the quick chart, backed by USGS 06200000 at Big Timber for official streamflow context.
Try
Check the Big Timber gauge first, then fish only if the river still shows enough clarity and side-pocket shape to read confidently.
Leave when
Skip or pivot when runoff spikes, thunderstorms muddy the river, wading feels marginal from the first entry, or cold spring weather turns the area into a survival project instead of a fishing day.

Flow and weather

Showing server-checked river conditions while current readings refresh.
Flow
76 cfs
From the latest stored river check. Open the official source for the newest reading.
Air forecast
51°F
Next 24h high
65.0°F

NWS air forecast near

Rain chance
43%

This is an air forecast, not a river-temperature reading. Check the water with a stream thermometer before fishing in hot weather.

Latest stored weather check

Chance Rain Showers

Wind
12 mph
Weather checked
More forecast and source details

Chance Rain Showers

National Weather Service

Boulder River forecast point

The National Weather Service forecast is temporarily unavailable.

Live data

Where these readings come from

RiverReports gauge: Boulder River at Big Timber

Official USGS station Opens in a new tab.RiverReports gauge Opens in a new tab.Official NWS forecast Opens in a new tab.

Flies for this time of year

Seasonal starting points, not a live hatch report. Match what you see on the water.

See flies for every season
SeasonWhat to look forFlies to try

Each fly name opens its matching Fly Box guide.

More fishing tips

Methods, fish species and trip notes

How to fish Boulder River today.

The Boulder is best from post-runoff summer into fall whenever the gauge shows enough shape for pocket water, bank edges, and faster riffle transitions without turning the river opaque or pushy. Skip it when spring melt, thunderstorms, or cold muddy color make every stop a visual guess.

Post-runoff drop

Usually the best mix of current, clarity, and bank definition for a full freestone day.

Stable summer flow

Good for pocket-water nymphing, attractor dries, and covering one area stretch well.

Fresh color after storms

Worth considering only if edges still read cleanly. Otherwise wait for the river to settle.

Heavy runoff

A clear skip signal because wading value and trout visibility both collapse quickly.

Wading, bank fishing or floating?
Access choicesNo single best option

Wading and Floating have the same top score. Use current access, footing, weather, and local rules to choose.

Wading74/100

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.

Floating74/100

A float is in play where this report supports boat access and wind, releases, and shuttle logistics are manageable.

Full river report

Is Boulder River worth the trip today? Check flow, weather, hatches, access, and rules for Montana before you go.

The Boulder is at its best when the river still carries healthy push but leaves defined banks, pocket seams, and crossing decisions that a wade angler can read. It turns into a pass quickly during runoff spikes, muddy color, or heavy weather that erases those edges.

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.
Seam
A seam is the line where fast and slow water meet.
Attractor fly
An attractor fly is bright or bold. It draws a strike without copying one exact insect.
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.
Dry-dropper
A dry-dropper rig has a floating fly with an underwater fly tied below it.
Pale morning dun (PMD)
Pale morning duns, or PMDs, are light-colored mayflies that often hatch in warmer months.
Why this call

Why this score

FlowUse caution

USGS shows 76 cfs. The flow has been stable over about 6 hours. USGS marks this reading provisional and may revise it. USGS records for this date (1948-2024, 76 readings) show a median near 134 cfs and the lower quartile near 80 cfs; today's flow is below normal for the date. This is below normal, so edge depth, temperature, and pressure matter.

SeasonHelps

Early fall: A strong technical window with cooler weather, cleaner flows, and lighter recreational pressure.

WeatherHelps

The current NWS air forecast is about 51F, and the next 24-hour high reaches about 65F. Chance Rain Showers.

Public alertsHelps

No active NWS alert was returned for this forecast point.

Fishing usefulnessHelps

Skip or pivot when runoff spikes, thunderstorms muddy the river, wading feels marginal from the first entry, or cold spring weather turns the corridor into a survival project instead of a fishing day.

Trip notes

Check these before you choose a reach.

Best flows

Use RiverReports and USGS 06200000 at Big Timber together. Stable post-runoff flow with clear edges and defined pocket water is the best signal. A rising muddy river or a broad heavy push should end the plan early.

When to leave

Skip or pivot when runoff spikes, thunderstorms muddy the river, wading feels marginal from the first entry, or cold spring weather turns the area into a survival project instead of a fishing day.

Local plan

Start with the Big Timber trend and one Main Boulder area section. Fish the first real pocket-water sequence hard, then let clarity, weather, and footing decide whether to move farther up the valley.

Backup water

If the Boulder is blown out, muddy, or too cold and pushy to wade cleanly, move to a larger river with steadier flow support instead of trying to outguess a freestone already saying no.

Boulder 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

Use Montana's current fishing rules for any district exceptions, then apply the stream-access law correctly: enter from legal public points and stay within the ordinary high-water mark rather than crossing posted private land.

Where to access the river

Main Boulder recreation area

Forest Service public area south of Big Timber with primitive roadside camping and easy river scouting.

Chippy Park Campground

A developed Forest Service campground with direct Boulder River access and a practical upper-area starting point.

Falls Creek Campground

A Forest Service campground farther up the Main Boulder road that works as a focused day-use or overnighter base.

  • Montana stream access helps once you enter legally, but the real trip-planning value comes from the named public area and campground entries.
  • The Main Boulder road gives you useful coverage, but this is still better as a one-section freestone day than a constant stop-and-go sprint.
  • Road and weather conditions can tighten the access window quickly in shoulder seasons, so check current conditions before a long drive south of Big Timber.

If this water does not fit the day, check another report before you start the drive.

MontanaYellowstone River fishing reportA lower-elevation backup near Big Timber when you need a larger river option.MontanaStillwater River fishing reportA freestone alternative if you want similar character with a different drainage.MontanaMadison River fishing reportA steadier fallback when you need more stable flow management than a runoff-prone freestone can offer.
See all Montana fly fishing reports

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.

See all 8 checked sources

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.

Source check is old. Last checked . Open the official links now and check for changes.

See something wrong? Report a source problem. Please do not send private spots or private access notes.

How this report was checked

How this report was checked

Trip guidance checked

What was checked: This Boulder River report is maintained from RiverReports and USGS Big Timber flow data, Montana FWP fishing regulations, stream-access law, Custer Gallatin National Forest Main Boulder and campground access pages, weather, generated-image disclosure, and runoff-sensitive freestone trout planning sources.

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

What should I check first on the Boulder River?

Start with RiverReports and USGS 06200000 at Big Timber, then decide whether the clarity and level still leave enough safe wading and readable current for a true freestone day.

Is the Boulder River mostly a float river or a wade river?

Most anglers treat it as a wade-first river from public area access rather than an all-day float commitment.

When should I skip the Boulder?

Skip it during heavy runoff, after storms that turn the river opaque, or whenever fast rising water removes the bank edges and pocket definition that make the river fish well.