December 2025 on The San Juan River

December on the San Juan River is one of the most overlooked gems in Western trout fishing. While most anglers see cold weather and assume slow fishing, those who actually fish the San Juan in winter know the truth: December is the start of big-fish season.

At About Trout, we spend more days on this river than we probably should admit. And right now? Despite colder mornings and off-color water, the San Juan is fishing hot, consistent, and far less crowded than peak season.

Here’s your full breakdown of December 2025 flows, visibility, hatch activity, and the flies you actually need.

Why December Is Quietly One of the Best Months on the San Juan

Winter on the San Juan River is a guide’s favorite time for a reason. The crowds thin out. The big fish slide into softer water. And the river settles into a stable, predictable rhythm.

Here’s what you can expect this month:

• Fewer Anglers

December is one of the least crowded months on the river. You’ll see more bald eagles than drift boats, and more empty parking lots than July ever dreams of.

• Big Fish Season

Cold temps don’t shut the fish down — they concentrate them. Nymphing gets deadly, and this is when trophy trout quietly slide into the net for anglers who stay patient and stay warm.

• Classic Off-Color Water

That signature “green tea” winter tint is here. The lake hasn’t fully turned over yet, so expect about two feet of visibility. Embrace it — the San Juan fishes extremely well in less-than-perfect clarity.

Current River Flows & Winter Forecast

Understanding flow is everything on the San Juan. It dictates depth, weight, drift speed, and how close you need to be to the bottom.

Here’s where we stand:

• Stable at ~300 CFS

The river is sitting right around 300 CFS, our typical steady winter release. No big spikes or drops expected — just consistent, reliable flows that make nymphing straightforward.

• Visibility Holding at Two Feet

Water viz is around 2 feet, classic pre-turnover clarity. Once overnight temps consistently freeze, expect the lake to flip and clarity to improve.

• Mild Early-December Weather

The first half of the month looks mild — but remember, this is the Southern Rockies. If you don’t like the weather… give it 15 minutes.

December Fly Selection: It’s a Nymphing Month

Let’s get honest: December on the Juan is 90% nymphing, 10% hoping for a dry window, and 0% trying to be a hero with a streamer.

Hot Subsurface Flies Right Now

The river is fishing a little “trashy” in the best possible way. Think big calories and easy meals.

Here are the flies you should NOT leave home without:

• Mops
• Leeches
• Eggs
• Red Larvae (yes, the OG San Juan Worm flavor)

These have been the mainstays in our rigs all week. With reduced clarity, fish want bold profile flies — and they will absolutely eat them.

Depth & Weight Matter More Than the Fly

With ~2 feet of viz, the priority is getting your flies down and keeping them there.

Recalibrate your depth and weight constantly.
If you’re not tapping bottom, you’re not fishing the San Juan correctly in December.

Dry Fly Opportunities: The Last Window of the Year

If you’re a dry fly angler, you still have a shot — but the clock is ticking.

Dry Fly Window: Now Through Mid-December

After mid-month, things tighten up. But right now you can still find consistent surface activity if you hunt for it.

Hatches to Watch

• Midge clusters (the water is covered in tiny heads right now)
• BWO (Baetis) hatches in the afternoon
• Calm days = magic
• Windy days = misery

The only thing killing the dry-fly action at the moment is wind. On calm afternoons, fish pod up and feed on top like it’s April.

Streamer Fishing: Manage Expectations

Streamer fishing has been spotty at best. You might turn a fish or two, but right now it’s far from consistent. If you want numbers or big-fish probability, nymphing beats everything else this month.

Winter Fishing Tips from the Guides

A few reminders to maximize your day:

• Dress warm. Layers are everything. Winter fishing rewards those who can stay on the water.
• Fish slow water. Trout conserve energy in winter — find soft edges and deeper buckets.
• Check weight constantly. Winter strikes are subtle and low in the column.
• Don’t ignore junk flies. This is the season they shine.

Final Word: Get Here Now

If you want:

• The last reliable dry fly fishing of the year
• Consistent action on nymph rigs
• Huge trout feeding in predictable winter lies
• A river that finally isn’t overrun with anglers

…then the first two weeks of December are your moment.

This is one of the most underrated, highest-reward times to be on the San Juan River.