June Fishing on the Stillwater River

June weather, stream flows, and summary

June on the Stillwater River will test an angler’s patience. Not because of challenging fishing, but because it is a guessing game as to when it will be safe to fish the river. In most years the Stillwater River comes into prime form in the second half of the month. In some years it happens sooner and in some years it happens later. 

The ability to fish the Stillwater River depends entirely on when snowmelt runoff peaks and stream flows begin to drop—keep in mind the catchment area for the Stillwater River is the highest, and snowiest plateau in Montana.

On average, the Stillwater River’s stream flows stabilize around 3,000 cubic feet per second (cfs) by June 15th. However, how high the stream flows run and how quickly the river drops and clears is a day-to-day prospect.

By early June snowpack data can paint a detailed picture to help forecast when in late June the Stillwater River may crest and begin to drop. Because the average annual peak streamflow occurs around June 10, by the second week of June the day-to-day forecast is the best gauge for when the river might come into form. 

The Stillwater River sees a diversity of weather patterns in June. Early June has an average daily high temperature hovering around 65 degrees F while later in the month average daily high temps tick close to 80 degrees F. Later in the month the prevalence of sunny days far out-weigh overcast days. Because the weather is varied in June, so is the river’s condition. If the first half of June is cold and rainy, snowmelt runoff is delayed, forcing anglers to wait until later in June for a fishable river. If the first half of June is warm and dry, snowmelt runoff may happen sooner, creating the possibility for the river to be in prime shape by June 15th.

When the Stillwater River becomes clear enough to fish, hatches of salmonflies, Golden stoneflies, and Yellow Sally stoneflies dominate. Golden stoneflies are an important hatch occurring shortly after salmonflies. Pale Morning Duns (PMDs) mayflies and various caddis species have a strong emergence in June. With a diverse array of hatching insects, late-June fly fishing on the Stillwater River can be consistent and action-packed—it is just necessary to be patient for the first couple of weeks of the month.  

June fishing: what to expect

In most years it is best to assume the Stillwater River will not be fishable until the second week of June. There are years when this isn’t the case and the river comes into shape sooner, or even later, but on average by mid-June the Stillwater River stream flows are holding steady around 3,00 cubic feet per second (cfs) and experienced floaters and anglers can find fish. It is also important to note that at stream flows above 2,500 cfs walking-and-wading angling is very difficult and dangerous. 

Once the Stillwater River drops below 3,000 cfs floating anglers can fish the dropping and clearing flows. But it is not until the river drops below 2,000 cfs that most floating anglers can safely float and fish the rivers fast, boulder-laden waters. Flows below 2,000 cfs often do not occur until July. 

Anglers planning to fish the Stillwater River in June can expect a river that is full, high, a bit off-color, and fished best with an expert boater at the helm of a raft. Because the Stillwater River is full of stonefly nymphs and the trout hang close to the bank for most of June, expectations can be good. 

Because the fish are holding near bankside structure, fish leaders that are short and stout—it is common to fish 7-foot 1X leaders with short tippets. For stonefly nymphs choose large black or brown patterns in sizes 2 to 8. For streamers, choose a tippet no less than 10 or 12-pound breaking test. For dry fly fishing, choose large dry flies in sizes 4 to 8. Be sure to fish a very stout tippet as well, nothing less than 10-pound test.  

Depending on stream flows, by late June Pale Morning Dun (PMDs) mayflies and caddis may begin to hatch. Leaders can be lengthened to 9-foot 4X and single dry flies in appropriate sizes to match hatching PMDs or caddis are ideal. 

Where to find June trout on the Stillwater

Finding trout on the Stillwater River in June depends on the volume of stream flows. By mid-June stream flows have dropped and stabilized around 3,000 cubic feet per second (cfs). It may take a few days for stream flows and clarity to be favorable for fishing, but when that occurs, salmonflies and Golden stoneflies can hatch in abundance. 

On the Stillwater River, salmonflies and stoneflies require structure from which to hatch. When an emergence of salmonflies and Golden stoneflies is strong, trout will be found near willows, submerged rocks and branches, and other structures. The fast and high flows in June force trout to hang near structure and in whatever slow water they can find. Stoneflies hatch by clinging to structure and then emerging from an exoskeleton, trout follow the insects and become opportunistic feeders as the current washes away the structure-clinging nymphs. 

By the last week of June—or when stream flows drop below 2,000 cfs—look for trout to migrate away from bankside structure or midriver structure and feed in riffles, below shelves and in riffle corners, and in pocket waters. These habitats are more favorable to the next round of abundant hatches, Pale Morning Dun (PMDs) mayflies and caddis. 

June, and especially late June, is gradually becoming prime time for the Stillwater River. As the mountain snowmelt from the Beartooth Plateau decreases throughout June, the river’s stream flows drop and clear. When this occurs trout on the Stillwater River can often be found anywhere a small break in the fast current occurs. 

Important June hatches

In most years snowmelt runoff peaks in mid-June and maintains a consistent stream flow for a few weeks. By the last week of June, stream flows often drop quickly so hatching insects can change daily. Because of this, the diversity of hatches during June is a huge part of the excitement of fishing this unique freestone. 

The salmonfly hatch is the most anticipated hatch in June on the Stillwater River. In most years, this hatch occurs in late June, but because the Stillwater River drains some of the highest country in Montana, whether river conditions allow for fishing is variable from year to year. In most years by June 20th, the river is hovering around 3,000 cubic feet per second (cfs) and has enough clarity anglers can effectively fish the salmonfly hatch. In some years the river is too high and too muddy and the fishing begins the last week of June and in other years the river drops and clears by June 10th. 

After salmonflies hatch, Golden stoneflies, Yellow Sally stoneflies, Pale Morning Duns (PMDs) and caddis dominate. After salmonflies and Golden stoneflies hatch, PMDs and caddis provide ample opportunities for dry fly fishing. 

Stillwater River fly box for June

Stonefly nymphs in brown and black in sizes 8 through 10

Salmonfly dry flies in sizes 4 to 8

Golden stonefly dry flies in sizes 6 to 10

Yellow Sally stonefly dry flies in sizes 10 and 12

Caddis pupae in sizes 10 to 16

Caddis dry flies in sizes 10 to 16

Pale Morning Dun nymphs in sizes 12 to 16

Pale Morning Dun emergers in sizes 12 to 16

Pale Morning Dun dry flies in sizes 12 to 16

Sculpin patterns in sizes 2 to 6

Streamers in olive, black or brown in sizes 2 to 6