Colorado has more than 6,000 miles of trout stream and 2,000 trout lakes, and summer is when nearly all of it is accessible. It is also the season with the most variables: runoff, monsoon thunderstorms, afternoon water temperature, and a fishing calendar that shifts by weeks depending on snowpack.
Runoff first, then everything else
Colorado's summer starts underwater. Snowmelt typically blows out freestone rivers from roughly late May through late June, with the peak and the duration set by that winter's snowpack and how fast it warms.
During runoff, most freestone rivers are unfishable — high, brown and cold. What still fishes:
- Tailwaters — rivers below bottom-release dams, where flow and clarity are controlled. These are your runoff insurance.
- Small high tributaries above the main snowmelt contribution.
- Lakes and reservoirs, which are unaffected.
By early to mid-July in a normal year, freestones drop into shape and the best fishing of the summer begins.
The South Platte
The most-fished trout water in the state and, for good reason, the most productive per mile.
Cheesman Canyon (Douglas and Jefferson counties, accessed from Deckers) is a technical, catch-and-release, gold-medal tailwater with large, extremely selective fish and a hike-in requirement that filters out casual traffic. Small midges and mayfly nymphs on light tippet.
Deckers itself, downstream, is more accessible and less technical, with excellent dry-fly fishing through summer.
The Dream Stream (Park County, between Spinney Mountain and Eleven Mile reservoirs, near Hartsel and Lake George) is a meadow tailwater running between two reservoirs, with large run-up fish and a well-earned reputation for wind.
Elevenmile Canyon, below Eleven Mile Reservoir, offers easier fishing and good access from Lake George.
The Arkansas River
Chaffee and Fremont counties, running through Buena Vista, Salida, Cotopaxi and Cañon City. Colorado's longest gold-medal water and one of the best freestone rivers in the West.
The Arkansas is a caddis river. The Mother's Day caddis hatch in late April and early May is the famous event, but summer fishing after runoff is arguably better: consistent hatches, wading access along Highway 24 and Highway 50 for miles, and enough water that you can find a run to yourself.
Summer patterns: a caddis or a stonefly dry with a nymph dropper, fished through pocket water and riffle seams. In late summer, hoppers along grassy banks.
The Arkansas is also a heavily used rafting corridor. Fish early, or fish the stretches upstream and downstream of the commercial rafting sections.
The Blue River and Summit County
Summit County, through Silverthorne, Dillon and Breckenridge. The Blue below Dillon Reservoir is a tailwater with cold, stable flows all summer — one of the more reliable options in July and August.
The stretch through Silverthorne, running past the outlet stores, is famous for large, well-fed and utterly jaded rainbows that eat mysis shrimp patterns and very little else. It is not easy fishing and it is not remote, but the fish are big.
The Fryingpan and the Roaring Fork
Pitkin and Eagle counties, out of Basalt, Aspen and Carbondale.
The Fryingpan River below Ruedi Reservoir is a fourteen-mile tailwater and one of the most celebrated trout streams in the country. Cold, clear, technical, and full of large rainbows and browns. Mysis shrimp, midges and small mayflies. Crowded, deservedly.
The Roaring Fork is a bigger freestone that joins the Fryingpan at Basalt and the Colorado at Glenwood Springs. After runoff it fishes beautifully with larger attractor dries, hoppers and streamers, and it holds more water per angler than the Fryingpan does.
The Gunnison
Gunnison and Montrose counties. The Taylor River below Taylor Park Reservoir holds famously large rainbows in its upper catch-and-release stretch. The East River and the main Gunnison through the valley offer excellent freestone fishing after runoff.
The Black Canyon of the Gunnison — accessed by steep, unmaintained routes from the national park, or by float through the Gunnison Gorge — is remote, physically demanding, and among the best trout fishing in the state for anglers willing to work for it.
High country lakes
From roughly mid-July through September, alpine lakes above 10,000 feet become ice-free and fish extremely well. Cutthroat, brook trout, rainbows and the occasional golden trout, in water that sees very few anglers.
The Indian Peaks, the Sawatch, the San Juans, the Flat Tops and Rocky Mountain National Park all hold dozens of them. These are fish that have a short season and see little pressure — a small attractor dry is usually all it takes.
Two cautions: afternoon thunderstorms in the Colorado high country are routine and genuinely dangerous above treeline. Be off the ridge by early afternoon. And altitude is real — 11,000 feet is not the place to discover you are not acclimated.
Warm water and the ethics of a hot August
This is the part that matters most.
Trout are stressed above about 68 °F and mortality climbs steeply past 70 °F, even with careful catch and release. In late July and August, lower-elevation Colorado rivers routinely reach those temperatures by afternoon, especially in a low-water year.
Colorado Parks and Wildlife issues voluntary fishing closures on specific reaches when conditions warrant, typically asking anglers to stay off the water after noon or entirely. Those advisories are published on the CPW website during the summer.
The practical rules:
- Carry a thermometer. It costs ten dollars and it is the difference between fishing responsibly and guessing.
- If the water is over 67 °F, stop, or move up in elevation.
- Fish mornings in August. By 1 p.m. on a hot day, quit.
- Watch for CPW voluntary closures and honor them.
- Land fish fast, keep them in the water, and use barbless hooks.
Going higher is almost always the answer. A river at 7,000 feet at 70 °F has a tributary at 9,500 feet at 55 °F, and the fish up there have not seen anyone.
Gold Medal water
Colorado designates certain stretches as Gold Medal Waters, meaning they meet standards for both trout biomass and the number of quality fish. The list includes reaches of the Arkansas, the South Platte, the Fryingpan, the Roaring Fork, the Gunnison, the Blue, the Colorado, the Rio Grande and several lakes.
Gold Medal stretches usually carry special regulations — often artificial flies and lures only, with restrictive or zero harvest. Those rules are posted and they are specific to the reach, not the river.
Before you go
Colorado fishing regulations vary substantially by reach, including artificial-only sections, catch-and-release-only water and specific bag limits. Colorado Parks and Wildlife publishes the current fishing brochure with reach-by-reach regulations, plus in-season voluntary closure notices during hot and low-water periods. Check both before you go.
Check your regulations before you go. Seasons, size limits, slot limits, bag limits and access rules change and vary by individual water body. Confirm the current rules with the relevant state or provincial fish and wildlife agency. Nothing on this page is a substitute for that.
