May Hatch Guide – Everything You Need to Know About Colorado Hatches in May
- brianchilbert
- May 7
- 4 min read
May is one of the most exciting months to be a fly angler in Colorado. It’s the transition from spring into early summer, and the rivers come alive with bugs, rising fish, and opportunity. With a warm spring and a lighter snowpack this year, we’re seeing hatches show up a little earlier than normal across the Vail Valley and surrounding waters. That means if you’re paying attention, you can get ahead of the curve and capitalize on some of the best fishing of the year.
Below is a full breakdown of the major hatches you need to know in May, along with timing, tactics, and the exact flies we’re using on our guided trips.
Caddis
Caddis are one of the most important food sources for trout in Colorado, and May is when things really start to ramp up. Expect strong emergences on the Eagle River, Roaring Fork, and Colorado River.
Timing:
Late morning into the afternoon, typically 11:00 AM through 4:00 PM, with peak activity depending on cloud cover and water temps. (Caddis will be more active on sunny days).
Tactics:
Start your day fishing larvae tight to the bottom in slower seams and deeper runs. As the hatch builds, transition to pupa patterns swung or dead drifted through riffles. Once you see adults fluttering, don’t hesitate to go dry.
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Go-to Fly Patterns (Sizes 18–14):
Larvae: Egans GTI Caddis, Hilbert’s Sexi Caddis
Pupa: Juan’s Kryptomite Caddis, Guide’s Choice
Adult: X-Caddis
Learn to tie “Hilbert’s Sexi Caddis Larvae”
Pro Tip:
During heavy emergences, fishing a pupa 12–18 inches off the back of a dry fly can be deadly.
Salmonflies
The most anticipated hatch of the year. Big bugs, aggressive eats and trout eager to take advantage of a big meal. With this year’s conditions, expect salmonflies to show up earlier than usual. (Salmonflies are usually only present on the upper stretches of the Colorado River.)
Timing:
Late May into early June, but watch for early movement this year. Best fishing is typically late morning through late afternoon.
Tactics:
Fish big nymphs early in the day before adults get active. Once you start seeing bugs flying and fish looking up, switch to dries tight to the banks, structure, and soft edges.
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Go-to Fly Patterns (Sizes 8–4):
Nymphs: Black Pat’s Rubber Legs
Dries: Fool’s Gold, Kurt’s Egg Drop Stone, Dornan’s Water Walker
Pro Tip:
Don’t be afraid to move your fly, twitching or popping your nymph or dry can invoke violent strikes.
Golden Stones
Golden stones often overlap with salmonflies and can provide consistent fishing before, during, and after the main event. (Golden Stones are present on nearly all of Colorado’s main rivers)
Timing:
Late May into June, often just behind or overlapping salmonflies.
Tactics:
Nymphing remains very effective, especially in faster water and pocket water. Dry fly fishing can be excellent along banks and structure when adults are present. A stonefly nymph should almost always be on your nymph rig this month.
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Go-to Fly Patterns (Sizes 10–8):
Pat’s Rubber Legs
Twenty Incher Stone
Rainy’s Cat Puke
Henry Fork Stone
Pro Tip:
Even if you don’t see adults, golden stone nymphs are always in play this time of year, especially on the Eagle, Colorado and Roaring Fork Rivers.
Blue Wing Olives (BWOs)
BWOs continue to be a key hatch, especially on cloudy or cooler days. They provide some of the most technical and rewarding dry fly fishing of the month.
Timing:
Midday into afternoon, often 12:00 PM to 3:00 PM, especially on overcast days.
Tactics:
Fish small nymphs leading up to the hatch, then transition to dries when fish begin to rise. Focus on softer water, tailouts, and eddies.
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Go-to Fly Patterns (Sizes 18–22):
Daysaver Baetis
Sexi Top May BWO
Parachute Adams
Pro Tip:
When fishing to trout rising for blue wings, long leaders and light tippet (5x–6x) make a big difference when fish get picky.
Midges
Midges are always part of the equation, especially in the morning before other hatches get going. Every river throughout the state will have midges present in the mornings. If you’re not sure where to start, thing on a midge pupa is a safe bet.
Timing:
Early morning through late morning, often peaking around 9:00–11:00 AM.
Tactics:
Fish small nymphs in slower water, deep runs, and tailouts. Don’t overlook midges just because bigger bugs are around.
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Go-to Fly Patterns (Sizes 18–22):
Daysaver Midge
Renegade
RS2
Pro Tip:
A midge dropper behind a larger attractor nymph can be a great way to pick off fish early in the day.
Runoff and Safety
May also brings rising water. As temperatures climb, snowmelt increases flows and can change river conditions quickly. High water can be dangerous. Always use caution when wading, be aware of changing flows, and don’t take unnecessary risks. When in doubt, fish from the bank or go with an experienced guide who knows the water. Want to take your white water skills to the next level? We have one spot left in our oar certification and guide school May 18th-22nd!
Fish With the Pros at Colorado River Outfitters
May is prime time. Between caddis, BWOs, and the start of stonefly season, this is one of the best opportunities all year to experience Colorado fly fishing at its highest level.
Want to learn more about entomology and how to match the hatch with confidence? Want to experience the salmonfly hatch from a drift boat with a front-row seat to explosive eats?
Book a trip with a Colorado River Outfitters guide.
Our team spends every day on the water dialing in these hatches so you don’t have to. Whether you’re a beginner looking to learn or a seasoned angler chasing a bucket-list hatch, we’ve got you covered.
Call or text today to lock in your date: 970-236-1937
Prime dates go fast, especially with everything running a little early this year. Don’t miss it!
Stay connected with Colorado River Outfitters for the latest fishing reports, hatch updates, fly tying tutorials, and on-the-water action from around the Vail Valley and beyond.
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Thank you for reading! We hope this blog helps everyone achieve success in the month of May!
Good luck out there!
-The CRO Team
