Fly fishing report · West

Big Thompson

A practical Big Thompson plan built around Rocky Mountain National Park rules, Big Thompson Canyon access, RiverReports flow support, and trout-friendly seasonal timing.

Check flow & weather

Today's river scoreHigh source confidence

Caution

Best option: Wade.

Wading is in play only where your chosen access has clear footing, legal entry, and no forced crossings.

Updated Jul 13, 11:17 PM UTCUsually refreshes about every 45 minutes

Recommended approachWade

Mode scores adjust the river-wide score for the risks of wading, bank fishing, or floating.

Wade · Best fit52/100

Wading is in play only where your chosen access has clear footing, legal entry, and no forced crossings.

Bank / edge52/100

Bank and edge fishing remains a practical low-commitment option if access is legal and footing is safe.

FloatCheck

This report does not describe this as a primary mode. Verify legal access, depth, launches, and retreat options before planning around it.

Confirm before you leave

Flow and weather right now.

Use the flow trend to confirm the score before you leave. Weather can change the safest and most productive fishing window.

River strategy

Treat this as a reach-by-reach canyon trout day.

The Big Thompson fishes best when you match your reach to runoff, canyon safety, and the current Rocky Mountain National Park or Colorado special-regulation section you actually plan to fish.

Use RiverReports for quick flow shape, then use USGS 06741510 as the official downstream flow check before committing to the canyon.
Inside Rocky Mountain National Park, special rules apply and several upper reaches are catch-and-release or closed; check the park page before you rig.
From Lake Estes downstream to Waltonia, Colorado lists artificial flies and lures only with immediate trout release, so rig barbless and keep handling short.
Skip the day during muddy runoff pulses, thunderstorm spikes, or if canyon pullouts and crossings force rushed wading decisions.

Why this score moved

FlowUse caution

USGS shows 63 cfs with a stable over about 6 hours trend. same-date USGS history (1979-2025, 47 readings) puts normal around 83 cfs and the lower quartile near 64 cfs; today's flow is below normal for the date. This is below normal, so edge depth, temperature, and pressure matter.

HeatUse caution

The NWS forecast is near 85F. Fish early and verify water temperature where trout stress is possible.

Public alertUse caution

An Air Quality Alert is active near this forecast point, so the score is capped below great until smoke and access conditions are checked. NWS alert: Air Quality Alert issued July 13 at 4:10PM MDT by NWS Denver CO.

Best mode nowUse caution

Wade: Wading is in play only where your chosen access has clear footing, legal entry, and no forced crossings.

SeasonHelps score

Summer: Primary dry-dropper season, especially mornings in the canyon and park meadow water.

Read the water

What changes the plan.

Stable summer and early fall flows usually offer the cleanest all-day trout fishing. During runoff, target softer seams and shorter sessions, and when the canyon is rising fast, choose another Front Range option.

Low clear water

Fish early and late with smaller dries, light nymphs, and longer leaders.

Moderate stable flow

Best all-around pocket-water condition for dry-dropper coverage.

Runoff or storm color

Stay near soft banks and eddies, fish bigger nymphs or streamers, or wait for the drop.

Warm afternoons

Lower canyon water can warm quickly; carry a thermometer and end the trout plan if temperatures climb.

Field plan

Fish it with intention.

Best flows

Stable or dropping freestone flows with enough visibility to fish pockets and banks safely.

When to skip

Skip during muddy runoff spikes, lightning-heavy afternoons, or when lower canyon water is warm enough to stress trout.

Local plan

Base in Estes Park, check park rules and the lower gauge, then choose one upper reach and one canyon backup instead of trying to cover the entire river.

Backup water

Shift to Boulder Creek, Clear Creek, or a South Platte option if runoff or canyon safety does not line up.

Hatches & flies

Bring a flexible box.

TimingWhat to watchUseful flies

SpringMidges, BWOs, small stones, and caddisZebra midge, pheasant tail, BWO emerger, black stone nymph

Reviewed pattern · report says “Zebra midge”Zebra MidgeLook for a very slim tapered thread body, evenly spaced contrasting wire rib, a small bead, and no tail or wing. The reviewed classic is black with silver wire and a silver bead. Red, olive, brown, glass-bead, jig-hook, resin-coated, or tailed forms must remain labeled variations rather than replacing the classic identity.See photos & how to fish it

Reviewed pattern · report says “pheasant tail”Pheasant Tail NymphThe pilot page distinguishes the sparse original idea from the bulkier American form. Both use pheasant-tail fibers and copper wire, but bead heads, peacock-herl thoraxes, legs, flashbacks, jig hooks, and soft-hackle collars are variations that must be labeled.See photos & how to fish it + 2 more reviewed guides in the Fly Box

SummerPMDs, yellow sallies, caddis, ants, and beetlesElk hair caddis, PMD cripple, yellow stimulator, foam ant

Reviewed pattern · report says “Elk hair caddis”Elk Hair CaddisLook for a tented elk- or deer-hair wing, clipped hair head, dubbed body, rib, and hackle palmered along the body. The body color should be labeled because tiers often match different natural caddis colors.See photos & how to fish it

Reviewed family · report says “PMD cripple”Pale Morning Dun PatternsPMD names an insect group, not one fly. Pale nymphs, trailing-shuck emergers, upright or low-riding duns, cripples, and spent-wing spinners stay visibly separate.See family guide + 2 more reviewed guides in the Fly Box

Late summerTerrestrials and evening caddisHopper-dropper, beetle, ant, soft hackle caddis

Reviewed family · report says “beetle”Beetle PatternsBeetle flies range from simple foam shells to hair-bodied and sunken forms. A rounded back and compact profile distinguish the family from ants and hoppers.See family guide

Reviewed family · report says “ant”Ant PatternsAnt patterns can be foam, fur-bodied, winged, or sunken. The narrow waist and paired body lobes matter more than one material recipe.See family guide + 1 more reviewed guide in the Fly Box

FallBWOs, midges, and streamer windowsRS2, midge larva, olive bugger, small sculpin

Reviewed pattern · report says “RS2”RS2Start with the beadless architecture: two dark-dun Microfibett tails separated behind a slim, tightly twisted and visibly segmented dubbed abdomen; a fuller thorax; and saddle-hackle web clipped into a short angled wing bud. Rim Chung's original-style form uses natural beaver dubbing and hackle web. CDC- or Antron-wing ties, beads, curved hooks, flash, and tailless Avatar-style flies must remain labeled variations.See photos & how to fish it

Reviewed family · report says “midge larva”Midge Patterns by StageMidge wording can mean a threadlike larva, wing-padded pupa, film emerger, tiny adult, or visible cluster. Those profiles fish at different depths.See family guide + 2 more reviewed guides in the Fly Box

Start with short, high-percentage pockets before you cast to long obvious runs.

In Moraine Park and other flatter upper reaches, make the first cast count and avoid lining fish in clear water.

When the flow is pushy, fish softer banks, inside seams, and depth changes instead of trying to reach the heavy middle current.

Move often. The Big Thompson rewards a steady string of short productive stops more than one long stationary session.

Access & responsibility

Know the entry. Know the exit.

Rocky Mountain National Park requires a Colorado fishing license for anglers 16 and older and lists specific catch-and-release and closed waters. Colorado's special-regulation page also lists the Big Thompson from the base of Olympus Dam at Lake Estes downstream to Waltonia as artificial flies and lures only with immediate trout release.

Moraine Park

Classic Rocky Mountain National Park meadow water; check current park access and reach-specific fishing rules first.

Lake Estes to Waltonia corridor

Special-regulation canyon stretch with many short stops, but parking and shoulder safety decide which pullouts are worth fishing.

Lower canyon near Loveland

Best used as a short-session option when the upper river is too crowded or still dropping.

Transparent sources

Check the facts behind the plan.

Last material review: 2026-05-31

flowRiverReports: Big Thompson flowUSGS Big Thompson River at Loveland safetyNWS forecast point near Big Thompson regulationRocky Mountain National Park fishing rules accessRocky Mountain National Park directions and US 34 access regulationColorado special fishing regulations safetyColorado Parks and Wildlife water safety

Common questions

Before you leave.

Is the Big Thompson a wade river or a float river?+

This page is primarily a wade plan. Most anglers do best by fishing short public sections rather than trying to float the canyon.

Which flow source should I trust first?+

Use RiverReports for quick trend reading and USGS 06741510 for official context, then adjust for the specific reach because upper park water can look different from the lower canyon.

What is the most important regulation check?+

Check both Rocky Mountain National Park fishing rules and Colorado's special-regulation page if your day crosses the park boundary or the Lake Estes to Waltonia stretch.