The Starting Lineup: 3 Flies You Must Have for September With CRO Guide Matthew Fletcher

September on the Upper Colorado is one of the most exciting times to be on the water. The mornings are crisp, the afternoons still carry a hint of summer warmth, the cottonwoods and willows are just starting to flash their golden hues. More importantly, the trout are hungry—feeding aggressively as they prepare for the colder months ahead.

With so many hatches and food sources available this time of year, fly selection can feel overwhelming. Just like a ball coach setting the lineup before a big game, you only need a few reliable players to make the day a success. Here are three flies I consider “must-haves” in September, whether you’re fishing the Colorado River, Eagle, or any freestone stream in the Rockies.

1. Juju Baetis (Size 18–22)

If there’s one insect you can count on in September, it’s the Blue Wing Olive (BWO). Baetis nymphs make up a huge portion of the trout’s diet during this shoulder season, and the Juju Baetis is a near-perfect imitation. Its slim, segmented profile matches the natural insect beautifully, and its durability means it can survive fish after fish.

How to fish it:

• Rig it under a hopper-dropper setup below a perdigon or frenchie for late morning or mid-day action.

• Drop it deeper under a strike indicator if you’re targeting riffles or runs where trout are holding lower.

• Fish it in tandem with a smaller midge or baetis emerger to cover multiple stages of the hatch.

If you see BWOs fluttering above the water—or even if you don’t—this fly is always a safe bet.

A beautiful Colorado River brown trout that fell for a juju baetis drifted through a shallow riffle.

2. Purple Haze (Size 18–22)

Some folks call it a Parachute Adams in purple clothing, but whatever you call it, the Purple Haze is one of the most versatile dry flies in Colorado. From technical tailwaters to high-country creeks, trout eat this pattern with confidence.

Why it works: The purple body offers just enough contrast to make it stand out, while still looking buggy and natural to trout. It’s visible to anglers, easy to track on the surface, and downright deadly when trout are sipping emergers or duns in slower water.

Best water types:

• Slow-moving bubble lines where fish rise delicately.

• Side channels and back eddies.

• Pocket water, especially if you’re prospecting.

Anytime you’re unsure what trout are keyed in on, tie on a Purple Haze. More often than not, you’ll get an answer quickly.

Another beautiful brown trout that sipped a purple haze in a foamy back eddie.

3. Kreelex Minnow (Streamers)

September isn’t just about tiny bugs—cooler water temps and shorter days also flip the switch for predatory behavior in trout. That’s when the Kreelex Minnow comes off the bench and earns its spot in the lineup. With its flashy body and heavy eyes, this streamer has the two things trout can’t resist: movement and shine.

How to fish it:

• On a floating line with a simple cast-and-strip retrieve.

• Along banks, structure, or drop-offs where trout are waiting to ambush.

• With short, erratic strips to make that jigging motion irresistible.

It’s especially effective on overcast afternoons when fish are willing to move for a bigger meal.

Matt Fletcher’s Pro Tip

“Think of September like a buffet. Trout have tons of options, but they’ll always go back for what’s familiar and easy to grab. Match the BWOs with a Juju Baetis, keep a Purple Haze ready for risers, and don’t be afraid to swing for the fences with a Kreelex Minnow. Between those three, you’re covered from sunup to sundown.”

Final Thoughts

Fly fishing in September is all about adaptability. Hatches can change by the hour, weather shifts quickly in the Rockies, and trout can move from sipping in slow seams to chasing streamers along the banks in the span of a day. But with this starting lineup in your box—the Juju Baetis, the Purple Haze, and the Kreelex Minnow—you’ve got the versatility to handle whatever the river throws your way.

So lace up your boots, pack some extra layers, and hit the water with confidence. The trout are waiting.

Stay connected with us on Instagram @colorado.river.outfitters for daily fishing updates, stunning river photos, and a behind-the-scenes look at our guides in action. It’s the best way to follow along with current conditions, fly recommendations, and all the incredible moments happening on the water. If you’re ready to book your next adventure with the Colorado River Outfitters team of exceptional guides, click the link below or give us a call at 970-236-1937—we’ll take care of the rest.

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