Fly fishing report · West

North St. Vrain

A Button Rock-focused North St. Vrain planning page built around walk-in access, permit-aware fishing, clear-water tactics, and Front Range backup decisions.

Check flow & weather

Today's river scoreMedium source confidence

Poor

Best option: Float.

A float can fit better than wading only if launches, shuttle, boat skill, wind, and local rules all check out.

Updated Jul 13, 11:17 PM UTCLive sources checked regularly

Recommended approachFloat

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

WadeCheck

Wading is the most sensitive plan today. Use protected edges only, avoid crossings, and downgrade quickly if clarity or current feels wrong.

Bank / edgeCheck

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

Float · Best fit23/100

A float can fit better than wading only if launches, shuttle, boat skill, wind, and local rules all check out.

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

Plan the walk and the permit rules before you plan the flies.

The North St. Vrain below Button Rock is most useful when you treat it as a walk-in creek with clear access boundaries, pressure-aware presentations, and a backup option if the preserve is busy or the water is running too hard.

Use RiverReports for quick flow context, then match the day to Button Rock Preserve access rules and the forecast.
The City of Longmont preserve page gives the clearest public access and seasonal-use framework for this reach.
Fish the creek quietly with short drifts and light rigs; the walk-in setting does not make the trout careless.
Do not confuse creek access with the separate Ralph Price Reservoir permit program when choosing where to spend the day.

Why this score moved

Best mode nowLowers score

Float: A float can fit better than wading only if launches, shuttle, boat skill, wind, and local rules all check out.

FlowUse caution

RiverReports is linked for the flow chart, but this page does not have a structured live flow value the score can read automatically. Treat the rating as conservative and open the chart before committing.

HeatUse caution

The NWS forecast is near 89F. 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.

SeasonHelps score

Summer: Primary season for early dries, caddis, terrestrials, and quick morning sessions.

Read the water

What changes the plan.

Late spring after runoff begins settling, summer mornings, and early fall are usually the best planning windows. Preserve crowding and exposed sunny afternoons can narrow the useful fishing window faster than the map suggests.

Low clear water

Use fine tippet, stay low, and fish smaller dries or light droppers along seams and banks.

Moderate stable flow

Best all-around condition for dry-dropper fishing and short nymph drifts.

High or pushy flow

Treat the creek as a bank-first scouting day or move to a safer backup if footing disappears.

Hot sunny afternoons

Fish early, monitor temperature, and shorten handling on pressured Front Range trout water.

Field plan

Fish it with intention.

Best flows

Stable clear flows that leave seams and bank pockets readable without forcing aggressive crossings.

When to skip

Skip when the preserve lot is full, summer heat is building, or the creek is too pushy to fish from safe edge positions.

Local plan

Get there early, fish creek water near the entrance first, decide whether the walk farther in is earning value, and keep Big Thompson or Boulder Creek ready as backups.

Backup water

Big Thompson, Cache La Poudre, or Boulder Creek are better pivots when Button Rock access, heat, or crowds narrow the day.

Hatches & flies

Bring a flexible box.

TimingWhat to watchUseful flies

SpringMidges, BWOs, and caddisRS2, zebra midge, BWO emerger, small caddis pupa

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 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 + 2 more reviewed guides in the Fly Box

SummerCaddis, PMDs, yellow sallies, and antsElk hair caddis, PMD dry, 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 dry”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 caddisBeetle, ant, hopper, soft hackle

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 + 2 more reviewed guides in the Fly Box

FallBWOs and midgesParachute BWO, RS2, zebra midge

Reviewed family · report says “Parachute BWO”Blue-Winged Olive PatternsBWO describes a hatch group, not one fly. Nymph, emerger, dry, cripple, and spinner profiles must stay separate because they occupy different parts of the water column.See family guide

Fish the first good-looking water you can reach legally because the creek near the entrance can be as useful as farther walk-in sections.

Stay off obvious banks and keep the first cast clean; preserve trout see plenty of hikers and anglers.

Use the creek for precision rather than distance, especially when other visitors are moving through the same corridor.

If the preserve parking lot is full or summer heat is building, pivot early instead of treating the walk as sunk cost.

Access & responsibility

Know the entry. Know the exit.

A Colorado fishing license is required, and the City of Longmont notes that Ralph Price Reservoir also requires a separate special permit with its own season and tackle rules. Review both the Colorado brochure and the preserve rules before you fish.

Button Rock Preserve entrance and fishing pier

Best official starting point for creek access and preserve orientation.

Longmont Reservoir side of the preserve

Useful for nearby walk-in water and mixed preserve scouting close to the entrance.

Ralph Price Reservoir approach

A two-mile hike and a separate permit context if you choose the reservoir instead of the creek.

Transparent sources

Check the facts behind the plan.

Last material review: 2026-05-31

flowRiverReports: North St. Vrain below Button Rock Reservoir safetyNWS forecast point below Button Rock accessCity of Longmont Button Rock Preserve accessCity of Longmont fishing information regulationCity of Longmont Ralph Price Reservoir Fishing Program regulationColorado fishing regulations regulationColorado fishing licenses and dates

Common questions

Before you leave.

Do I need a special permit to fish the creek?+

For the creek, start with a valid Colorado fishing license. The separate special permit applies to Ralph Price Reservoir inside Button Rock Preserve.

Is the best fishing far inside the preserve?+

Not always. Water close to the entrance can fish well, especially when you can work it quietly before foot traffic builds.

What is the biggest planning mistake here?+

Mixing up preserve access rules, reservoir permit rules, and creek strategy. Sort those out before you choose flies.