Yellowstone River Fishing Report: Autumn Arrives, Trout Wise but Rewarding

This is Artificial Lure coming to you with the Yellowstone River fishing report for Saturday, September 13th, 2025.

Sunrise hit the water at 6:56 AM this morning, and we’re looking at sunset around 7:34 PM. No tidal movement here on the Yellowstone—she’s a free-flowing river, but flows are holding steady and the river is running clear, which is just what we want for some classic September fishing in Montana.

The weather is turning a little more autumn-like as we head deeper into September. Expect daytime highs in the mid-60s, dipping near the low 40s at night, with partly cloudy skies and a light breeze out of the west. We might see a little rain pushing in later this weekend, which could color up some of the side channels, so keep an eye out if you’re fishing the Soda Butte or Lamar tributaries.

Fishing has been good on the Caldera stretch of the Yellowstone—this time of year, the trout that remain are big and have earned their stripes, so come with your A-game. Early mornings are best for technical dry fly fishing, targeting trout sipping rusty spinner patterns in sizes #12-18. As the sun gets up and things warm, you’ll see some fish rising for mayfly emergers, especially olives in #16-18, and don't overlook midges if the clouds hang around.

Terrestrials are still a solid bet on those sunnier afternoons—small ants and hoppers drifted tight to grassy, undercut banks are pulling some nice browns and cutthroat. The fish are definitely wise, so long leaders and perfect drifts will get you takes. For nymphing, a #16-18 beadhead pheasant tail or hare's ear under a small indicator is still working, especially in deeper runs below riffles.

According to Big Sky Angler, streamer action is heating up as a few more migratory fish start to move—tossing small articulated streamers or classic olive Woolly Buggers early morning or late evening can turn up a surprise brown or two. Fish these through the seams and along any drop-offs, especially as the river sees less pressure now that fall is here.

For recent catches, anglers are reporting healthy numbers of browns and cutthroat in the 14 to 18 inch range, with a few bigger fish landed by those willing to walk further from the main access points. The action isn’t always fast, but the quality puts this time of year near the top for Yellowstone regulars.

Hot spots today: Look for action at Carbella access just north of Gardiner, and steady reports are coming in from the Paradise Valley stretches around Mallard’s Rest. If you’re hunting that perfect dry fly eat, try the slower side channels just below Yankee Jim Canyon—these are holding good numbers of fish and getting less pressure.

Local shops recommend a 5-weight rod, nine-foot leader, and a fly box stocked with rusty spinners, olive and gray mayfly patterns, foam ants, and tan or pink hoppers. For the nymphers, pheasant tails and zebra midges will keep you in the game. For bait anglers on the lower stretches outside of park boundaries, nightcrawlers are still productive, but artificials are accounting for more of the bigger hookups.

Regulations note: All Yellowstone waters are open sunrise to sunset as per the 2025 Fishing Regulations, and the Hoot Owl closures have been lifted on area rivers.

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