What You'll Find on the Big Thompson

The Big Thompson River runs 85 miles from the Continental Divide near Estes Park down through the Front Range foothills to its confluence with the South Platte River near Loveland. The river holds native cutthroat trout in its upper reaches and brown trout throughout most of its accessible length, with some rainbow trout mixed in below the dam. Water clarity and temperature vary dramatically depending on which section you fish and what time of year you arrive — the upper canyon stays cold and swift, while the lower valley sections warm considerably by mid-summer.

The Big Thompson is split into distinct fishing zones by geography and access. The upper canyon section above Lake Estes is tight, technical water best suited to anglers comfortable with small flies and precise casting in confined spaces. The middle section from Estes Park downstream to the town of Drake offers a mix of pocket water and pools. The lower river below Drake widens and slows, becoming more approachable for waders of varying skill levels, though it also draws more pressure from the Front Range population centers nearby.

Key Takeaways

  • The Big Thompson holds cutthroat trout above Estes Park and brown trout throughout the lower and middle sections, with seasonal water temperature swings that affect where fish hold.
  • Access varies by section: the upper canyon requires hiking and scrambling, the middle section has roadside pullouts and short walks, and the lower river has public access points and easier wading.
  • Colorado Parks and Wildlife manages the river under statewide regulations; you need a valid Colorado fishing license and must follow species-specific possession limits and size restrictions.
  • Spring runoff (April through June) makes the river high and turbid; the best fishing windows are late June through September and again in October after water levels drop.
  • The Big Thompson can be crowded on weekends and holidays, especially near Estes Park and along Highway 34; weekday mornings and shoulder seasons offer quieter fishing.

Seasons and Water Conditions

Spring runoff dominates the Big Thompson from April through mid-June. Snowmelt from the high country turns the river brown and pushes water levels well above normal, making wading dangerous and fly presentation nearly impossible. If you fish during this period, focus on the lower sections below Drake, where the water clears slightly faster and flows are more manageable. Nymphs fished deep in slower pockets are your best bet, though success is never may provide.

Summer (late June through August) brings the most reliable fishing. Water levels drop to fishable heights, and the river clears enough to see structure. Daytime temperatures can push the lower river into the 60s Fahrenheit by mid-July, which slows the bite during midday hours. Fish early morning and late evening, or focus on shaded canyon sections where water stays cooler. Dry fly fishing becomes viable in July and August, particularly in the mornings and during evening caddis hatches.

Fall (September through October) offers excellent conditions. Water temperatures cool, fish become more active throughout the day, and the summer crowds thin considerably. October is often the best month on the Big Thompson — water is clear, flows are stable, and you can fish productively from mid-morning through late afternoon. By November, water temperatures drop below 50 degrees and fishing slows, though it remains possible on warmer days.

Winter fishing is possible but difficult. The river rarely freezes solid, but ice forms along the banks and in eddies. Water temperatures in the 30s and 40s Fahrenheit push trout into the deepest, slowest pools. If you fish in winter, focus on midday hours when temperatures are highest, fish nymphs very slowly in deep water, and expect fewer and smaller fish.

Access Points and Parking

The upper canyon section above Estes Park requires hiking to reach. The Cascade Creek trailhead and Emerald Lake trailhead both provide access to cutthroat water, but expect a 2- to 4-mile hike one way. These sections are remote and see light pressure, but the water is small and technical. Park at the Rocky Mountain National Park visitor center or designated trailheads; day-use fees apply for national park access.

The middle section from Estes Park to Drake has several roadside pullouts along Highway 36 and Highway 34. The town of Estes Park itself has public access points, including the Estes Park Fishing Ponds and sections along the Big Thompson Avenue corridor. Below Estes Park, pullouts near the town of Drake provide access to wider, slower water that is easier to wade. These areas see moderate to heavy weekend traffic.

The lower river below Drake has public access at several points. The Loveland area offers access near the confluence with the South Platte, and there are pullouts along Highway 34 between Drake and Loveland. The Big Thompson Confluence area near Loveland is the most accessible and most crowded section. Parking is usually available at marked pullouts, though spaces fill quickly on weekends.

Private land borders much of the Big Thompson. Always ask permission before crossing private property, and respect posted no-trespassing signs. Some sections are accessible only through outfitter-guided trips or by paying day-use fees to private landowners.

Regulations and Licensing

You must have a valid Colorado Parks and Wildlife fishing license to fish the Big Thompson. Licenses are available online at Colorado Parks and Wildlife's website, at sporting goods stores, and at many convenience stores throughout the state. A one-day license costs less than a full-year license if you plan only a single trip.

The Big Thompson is managed under Colorado's statewide fishing regulations. Cutthroat trout have a daily possession limit of 10 fish with no minimum size requirement in most sections, though some upper canyon areas have special restrictions — check the current Colorado Parks and Wildlife fishing guide before you go. Brown trout have a daily possession limit of 10 fish, with a 16-inch minimum size requirement in most sections. Rainbow trout follow the same limits as brown trout where they are present.

Artificial flies and lures are allowed throughout the river. Bait fishing is also legal in most sections, though some upper canyon areas restrict it. Check the current regulations for the specific section you plan to fish, as restrictions can change year to year.

The Big Thompson is open year-round, but conditions and fish availability vary dramatically by season. Winter fishing is legal but often unproductive.

What Flies and Tackle Work Best

The Big Thompson responds well to small flies. In the upper canyon sections, use size 16 to 20 dry flies during summer hatches, particularly small caddis imitations and Adams patterns. Nymphs in sizes 14 to 18 — pheasant tails, hare's ears, and small stonefly nymphs — work year-round in pocket water and deeper pools. Cutthroat trout in the upper river are less selective than brown trout and will take a wider range of patterns, but presentation matters more than exact imitation.

In the middle and lower sections, brown trout demand more precision. Use size 12 to 16 dry flies during caddis hatches (typically June through August) and mayfly hatches (sporadic throughout the season). Nymphs in sizes 12 to 16 work well fished on a dead drift or with a slight twitch. Streamers in sizes 2 to 6 — black woolly buggers, sculpin imitations, and small baitfish patterns — can produce larger fish, especially in early morning and late evening.

A 4-weight to 5-weight fly rod is standard for the Big Thompson. The upper canyon sections benefit from a shorter rod (7 to 8 feet) for tight casting, while the middle and lower sections work well with a standard 9-foot rod. Use a 4x to 5x tippet for dry flies and a 3x to 4x tippet for nymphs and streamers. The water is relatively clear, so fine tippets help, but the rocky bottom and snags mean you will lose flies regularly — carry plenty of spares.

When the River Is Too High or Too Crowded

If the Big Thompson is running high and muddy during spring runoff, consider the South Platte River near Deckers or the North Fork of the South Platte, both of which clear faster and offer similar brown trout fishing. The Cache la Poudre River near Fort Collins is another alternative that often clears before the Big Thompson.

If weekend crowds are too heavy, fish on weekday mornings, particularly Tuesday through Thursday. The upper canyon sections above Estes Park see far less pressure than the roadside pullouts, though they require more effort to reach. October is the best month to avoid crowds while still finding good fishing conditions.

If you want to fish the Big Thompson but prefer guided instruction or want to learn the water faster, several outfitters in Estes Park offer guided trips. These trips are not inexpensive, but they provide access to private sections and local knowledge that can shorten your learning curve.

Frequently Asked Questions

Do I need a Colorado Parks and Wildlife stamp in addition to my fishing license?

No. A Colorado fishing license is all you need to fish the Big Thompson. Some special use areas or national parks may have additional fees, but the river itself requires only a valid state license.

Can I fish the Big Thompson in winter?

Yes, the river is open year-round. Winter fishing is legal but difficult — water temperatures are cold, fish are sluggish, and ice forms along the banks. If you fish in winter, focus on deep pools during midday hours and use very slow nymph presentations.

What is the best time of year to visit if I am a beginner?

Late June through September is ideal for beginners. Water levels are manageable, temperatures are comfortable, and fish are active. The lower sections below Drake are easier to wade and more forgiving than the upper canyon. Avoid spring runoff (April through June) and plan your trip for a weekday if possible.

Are there fish in the Big Thompson year-round?

Yes, but their location and activity level change with the season. Summer and fall offer the most consistent fishing. Winter fish are concentrated in deep pools and are less active. Spring runoff pushes fish into slower water and makes them harder to catch.

Can I use bait on the Big Thompson?

Yes, bait fishing is legal in most sections of the Big Thompson. Check the current Colorado Parks and Wildlife fishing guide for any special restrictions in the specific area you plan to fish, as some upper canyon sections may have fly-only or artificial-only rules.