Rio Grande Fly Fishing Report - August 8/23/2025
RIO GRANDE FLY FISHING REPORT
San Luis Valley & Upper Rio Grande Basin — Late Summer Conditions
Report Date: August 23, 2025 | Next Update: August 30, 2025
Current River Conditions
Flows are in typical late‑summer levels and many stretches are fishable from bank and boat. Water clarity is generally good; expect lower water in warm afternoon hours and cooler seams near springs and tributary inflows. Watch for warm water pockets — target early mornings and evenings for the best dry‑fly action.
Flows & Clarity
Late‑summer flows: generally low to moderate (typical seasonal drop).
Clarity: Mostly clear to slightly stained in upper riffles after thunder showers.
Notes: Late‑August thunderstorms can spike small tributaries — be alert for sudden color and increased current.
Late‑summer flows: generally low to moderate (typical seasonal drop).
Clarity: Mostly clear to slightly stained in upper riffles after thunder showers.
Notes: Late‑August thunderstorms can spike small tributaries — be alert for sudden color and increased current.
Water Temperature
Typical late‑Aug range: cool spring pockets (50s°F) to warmer runs (mid‑60s°F).
Trend: Rising daytime temps through the month; fish deeper runs if surface temps climb.
Typical late‑Aug range: cool spring pockets (50s°F) to warmer runs (mid‑60s°F).
Trend: Rising daytime temps through the month; fish deeper runs if surface temps climb.
Angling Access
Access points: most public access is open; private landings require permission.
Road & trail: dry and firm, but short hikes still recommended to reach quiet runs.
Fisheries rules: check local regs — many Rio Grande Cutthroat areas require single, barbless hooks and specific bag limits.
Access points: most public access is open; private landings require permission.
Road & trail: dry and firm, but short hikes still recommended to reach quiet runs.
Fisheries rules: check local regs — many Rio Grande Cutthroat areas require single, barbless hooks and specific bag limits.
Target Species
Rio Grande Cutthroat, Brown and Rainbow trout where stocked or connected, plus holdover native trout in high country tributaries.
Best action: early morning and evening for sight‑fishing; subsurface nymphing productive mid‑day.
Rio Grande Cutthroat, Brown and Rainbow trout where stocked or connected, plus holdover native trout in high country tributaries.
Best action: early morning and evening for sight‑fishing; subsurface nymphing productive mid‑day.
Hatch Chart & Insect Activity (Late Aug)
| Insect | Size | Activity | Where to Look |
|---|---|---|---|
| Terrestrials (hoppers, ants) | #6–12 (bulk) / larger hoppers | High — especially late morning to early evening | Slow edges, willow lines, riffle tailouts |
| Caddis | #14–18 | Moderate — best in evening skittering & emergers | Fast water margins, near woody debris |
| Blue‑winged olives (BWO) / Small mayflies | #16–20 | Light to moderate — mornings and cool afternoons | Shallow riffles & soft seams |
| Midges | #18–22 | Consistent — all day in calmer pools | Smooth tailouts, deep slow runs |
| Stoneflies / Salmonflies | #6–10 / #4–8 | Low — main spring/early summer window has passed; occasional late stonefly pockets possible | Large cobble runs and faster whitewater (higher elevation tributaries) |
Recommended Flies (Patterns & Links)
Below are hand‑picked patterns that match what trout are eating now. Click each pattern to view the fly and order if you need to top up your box.
Dry Flies & Terrestrials
- Fancy Pants Hopper - Tan — go‑to hopper for late summer foam lines and bank breakers.
- Corn‑fed Caddis (CDC) - Tan — skittering evening caddis and emergers.
- Parachute - Blue Wing Olive (BWO) — a reliable small mayfly when fish key to light mayfly action.
- Libby's Salmonfly — carry a couple for late spring/early pockets in higher tributaries; sometimes fish key on large stonefly imitations in slack summer runs.
Nymphs & Subsurface
- Tungsten Pat's Rubber Legs — cornerstone for big trout on stonefly/nymph drifts.
- Pheasant Tail Tungsten — universal mayfly nymph; fish it weighty and deep.
- Tungsten Split Case Nymph - PMD — great when PMD nymph activity is present.
- Black Zebra Midge (TBH) — midge concentrations in calm pools and deep slack water.
- Olsen's DNA Worm - Brown & Red — subtle worm/dirty fly for finicky late summer trout.
Streamers & Big Patterns
- Coffey's Articulated Sparkle Minnow - Sculpin #4 — fish this through deeper runs and structure for aggressive takes.
- Sculpzilla - Natural — excellent for low light and pulling trout out of holding water.
- Sunny Side Up - Sunburst (Egg) — especially effective below spawning tributaries and when trout key on eggs or orange targets.
Tactics & Quick Tips
Early morning: target cool seams and rise lanes with dries (hopper + small mayfly patterns).
Midday: indicator nymph rigs with a heavy tungsten nymph (Pheasant Tail or Pat's) ahead of a softer dropper; fish deeper pockets and tails of runs.
Evening: skitter Caddis patterns and terrestrials along banks; watch for selective takes and short touchdowns.
Streamer work: slow strips through current seams and along structure; pause and let the fly swing through tailouts. Big brownies and cutthroat respond when water is cooler or after sundown.
Midday: indicator nymph rigs with a heavy tungsten nymph (Pheasant Tail or Pat's) ahead of a softer dropper; fish deeper pockets and tails of runs.
Evening: skitter Caddis patterns and terrestrials along banks; watch for selective takes and short touchdowns.
Streamer work: slow strips through current seams and along structure; pause and let the fly swing through tailouts. Big brownies and cutthroat respond when water is cooler or after sundown.
Local Notes & Safety
- Regulations: confirm current season rules for Rio Grande Cutthroat protection zones; many areas require barbless hooks and have special harvest rules.
- Weather: high‑valley afternoons can produce thunderstorms; plan to exit the water early if storms approach.
- Conservation: pack out all leaders and tippet, minimize wading in spawning gravels, and use streamwise approaches to reduce bank erosion.
- Guides & Shops: call a local fly shop or guide if you want the freshest report for a specific reach — they will have day‑to‑day intel on water clarity and access gates.
