September has arrived in Yellowstone Country, bringing longer nights, chilly mornings, and the first signs of fall fishing in the Park. We’re looking at a pleasant stretch of early September weather through much of the upcoming week, with comfortable afternoons and increasingly cold overnight temperatures.

There are signs of another change beginning late this weekend, with the potential for cooler, wetter weather returning Sunday into Monday. This time of year, a cool, cloudy weather system can quickly change the complexion of the fishing, bringing Baetis and other fall mayflies into play.

Update: Yellowstone lifts full closures for Firehole, Madison and Gibbon rivers

Effective Friday, Aug. 28, anglers can fish the Firehole, Madison and Gibbon (downstream of Norris Campground) rivers and all associated tributaries from sunrise until 2 p.m. each day. Cooling weather and water temperatures, as well as precipitation in the current weather forecast, allow for the full closures to be lifted.

The full closures were implemented on July 15 because low water flows and high water temperatures exceeding 68 degrees Fahrenheit (20 degrees Celsius) can be lethal to fish. Water temperatures have cooled at night, allowing for fishing for part of the day. Anglers can fish on most other park rivers, streams and lakes daily from sunrise to sunset as specified in the 2026 Fishing Regulations booklet.

Staff will continue to monitor the water temperatures. Temporary restrictions may be lifted, or additional closures may be put in place, depending on condition assessments.

Anglers: Please fish during the coolest times of day and land fish quickly. Do not play hooked trout to exhaustion. Gently handle fish in the water as much as possible and let them recover before release. Your cooperation will protect the park’s fisheries and may prevent the need to prohibit fishing at all times of the day on some rivers and streams if conditions worsen. 

Keep an eye on Park closures HERE for the latest updates.

HERE'S THIS WEEK'S STANDOUTS. 

NORTHEAST CORNER – SLOUGH, SODA BUTTE & LAMAR

Last week's rains have raised flows and turbidity on the Lamar River and Soda Butte Creek, leaving both rivers off-color and largely unfishable at the start of the week. You can keep a close eye on the Lamar flows HERE. Conditions are slowly improving as flows drop and the water has a chance to clear.

In the meantime, Slough Creek will be a much better option, and the timing is right to take advantage of some of the first hatches of Fall Drakes (Timpanoga hecuba). These size #12 mayflies are an important late-season food source for opportunistic cutthroat and can provide some exciting sight fishing with large dry flies like JoJo’s Drake Mackerel or Baltz’s Hi-Vis Paranymph.

Keep an eye on the forecast as we head toward Sunday and Monday. Another round of cool, wet weather is possible, and any significant rainfall could quickly bring another pulse of dirty water to the Lamar River and Soda Butte Creek.

YELLOWSTONE RIVER – CANYON STRETCHES

The canyon stretches of the Yellowstone remain a great option for anglers willing to cover some ground and fish a variety of water. Terrestrials continue to be important, and hoppers like Pavlovich’s Sweet Dreams Hopper are a good choice for prospecting along banks, through riffles, and around structure.

If significant rain develops in the Northeast Corner late this weekend, remember that the Lamar River can affect clarity in the Yellowstone downstream from its confluence. Water upstream of the Lamar will remain unaffected, making the upper canyon stretches a valuable option when the lower river gets dirty.

YELLOWSTONE RIVER – CALDERA STRETCH

September marks a noticeable transition on the Yellowstone River in the Caldera. The number of large Yellowstone Cutthroat Trout remaining in the river continues to diminish as fish make their way back toward Yellowstone Lake, but there are still some impressive fish in the system for anglers willing to cover water and hunt for them.

Sight fishing remains the name of the game here. Morning spinner falls of small mayflies can provide opportunities when conditions are calm, making size #16–20 rusty and olive spinners important flies to carry. Flying ants like Heames’ Honey Ant and hoppers like KK’s Henneberry Hopper remain excellent options, particularly as the day warms and afternoon winds begin moving terrestrials around.

Sunny conditions make spotting these fish considerably easier. If clouds arrive with the anticipated weather change late this weekend, sight fishing will become more challenging, but those same conditions could bring Baetis and other fall mayflies like Heptagenia (size #16–18) into play.

GALLATIN RIVER

The Gallatin benefited from some cool, rainy weather this week with the start of some fall hatches of Baetis mayflies. As conditions warm back up this week you should find fish looking for hoppers and ants again. These dry fly eats are getting harder and harder to come by as the season rolls on. Increasingly, fish are holding in tighter and sneakier spots. Pay extra attention to undercut banks, and dark pockets below rocks or deadfall. Good drag free drifts are a must here now if you're hoping to fool the biggest of these sneaky fish who have seen plenty of flies by this point in the season. As always on the Gallatin, the best dry fly fishing will be in the late-mornings and afternoons after temps have had a chance to climb. Beforehand, nymph fishing larger runs and pockets can provide fun fishing.

Keep an eye on the forecast as we head toward Sunday and Monday. A return to cool, cloudy weather could shift the Gallatin away from terrestrials and provide another opportunity for Baetis.

EXPLORE THE BACKCOUNTRY

As we enter the start of September, it's still prime time to explore the backcountry of Yellowstone National Park. Trails have dried out, the peak of the biting fly season has passed, and meadows are alive with the buzzing and clicking of terrestrial insects.

For anglers willing to lace up their boots and hike into remote waters, few places offer more rewarding opportunities than Yellowstone. We’ll leave the joy of discovering these hidden gems to you; that’s half the fun, after all. But rest assured, all of our favorite fisheries in the Park begin somewhere in the backcountry. A little time spent poring over a map of these headwaters is almost guaranteed to lead to memorable fishing.

September weather does require a little more preparation. A warm, sunny afternoon can turn into a cold, wet evening remarkably quickly, and overnight temperatures are increasingly dipping toward freezing in the high country.

So grab your pack, lace up, and hit the trail. Backcountry fishing in Yellowstone is as much about the journey as it is the fish. 

BACKCOUNTRY ESSENTIALS

Whenever you venture into the Yellowstone backcountry, be prepared for rapidly changing conditions. At a minimum, we recommend carrying:

• Bear spray—and knowing how to use it
• Water and/or a water filter
• Sunscreen
• Insect repellent
• Rain jacket
• Extra warm layer, such as a lightweight puffy
• Basic first-aid kit
• Emergency snacks
• Map, digital or printed—and knowing how to use it.

As always, check in with the shop for the latest conditions, fly recommendations, and river updates. We’re here to help you stay dialed in for your next adventure!