July Fishing on the Gallatin River

July weather, stream flows, and summary

July on the Gallatin River is everything a trout river can be—prolific hatches, wade and float fishing options, and plenty of wild trout. It may seem too good to be true, but with 90 miles of wild trout water from Yellowstone National Park downstream near Big Sky and Bozeman and then its terminus at the confluence of the Jefferson and Madison Rivers to make the Missouri River, the Gallatin River is truly a gem. July sees hatches of stoneflies, caddis, and mayflies. Streamflows are often clear and consistent and weather is pleasant. 

Angling days in July are long, averaging just over 15 hours of daylight a day. The average daily high temperature of 80 degrees F reflects the long days of sunshine. Around 1.5” of accumulated precipitation falls in July, making it one of the driest months of the year. With these long, warm days fishing the Gallatin River can be good throughout the day, including early morning and late evening. 

In most years, snowmelt runoff is complete by the first week of July and streamflows drop and clear more and more each day. If June receives above average precipitation or is colder than average, snowmelt runoff on the Gallatin River may continue through the first week of July, but those years are rare. 

Fishing the Gallatin River in July means the entire river is an option. For fishing in July, the river is best broken down into four distinct sections: Yellowstone National Park, Gallatin Canyon, Galley Valley, and the float section downstream of the confluence with the East Gallatin River. 

The river in Yellowstone National Park is a meandering meadow stream. Consisting of willow-lined banks and riffles and pools, trout here are small and number considerably less than in the canyon section. As the river exits Yellowstone National Park, it gains flow from the Taylor Fork. Here it enters the Gallatin Canyon section. Defined by pocket water, fast runs, deep holes, and riffle-shelf-run water, this section is home to large populations of healthy trout in the 8 to 12-inch range. Larger fish are indeed found, but the canyon section on the Gallatin River is known for beautiful scenery and plenty of public access for the wade angler. As the river exits Gallatin Canyon—about 25 miles north of Big Sky—the Gallatin River takes on the feel of a valley river. Lined with tall cottonwoods its riffle-run nature is home to plenty of rainbow trout and the occasional big brown trout. Access points in this section are farther apart and anglers willing to walk a good way from an access can find plenty of lightly fished water. Below the confluence of the East Gallatin River fishing from a boat is allowed, however this section is not known for producing plentiful populations of trout. 

With its wide array of hatches and variety of types of water, the Gallatin River in July has something for every angler. Weather, streamflows, and hatches are often consistent and predictable, making the Gallatin River the perfect complimentary stream to some of Montana’s other more headline-grabbing destination rivers. 

July fishing: what to expect

From casting big dry flies to structure or dragging streamers through deep runs or dead-drifting two-fly weighted nymph rigs, something exists for all anglers to enjoy on a river in its prime summer-time mode. The Gallatin River in July features all the best attributes of Montana fly fishing. There are opportunities for catching fish using a variety of methods. 

Fishing in July on the Gallatin River is consistent, but it also varies throughout the month. A typical day in early July might look different than a typical day later in the month. In early July as Golden stoneflies, caddis, and PMDs dominate the hatch charts, fishing dry flies may be the best way to catch fish. Because the available hatches may run the gamut, having PMDs, caddis, and stonefly dry flies is a must. 

The river in Gallatin Canyon gains most of the focus early in July as this the most accessible section of the river as much of it flows through Custer-Gallatin National Forest. Additionally, populations of aquatic insects and wild trout are the highest here compared to other sections. 

As the second week of July comes and flows continue to drop, hatches of caddis and PMDs increase in frequency. The large riffle and run sections of the river in Gallatin Valley west of Bozeman become more angler friendly as flows drop. Two-fly weighted nymph rigs tied with a large stonefly nymph—size 8 or 10—and a size 12 or 14 Pheasant Tail or caddis pupae work well. 

Because July sees long, sunny days, it is important to know when to fish as much as it is where to fish. If large fish are desired, the lowlight hours of early morning and evening are often best for targeting large fish with streamers or dry flies. Even in the bright sun smaller fish may rise to a well-presented dry fly. Later in the month when grasshoppers begin to show up in streamside grasses, midday and late afternoon are ideal for prospecting with a terrestrial. Dry fly anglers can find surface action even in the bright sun of midday and afternoon on the Gallatin River. 

Where to find July trout on the Gallatin River

As streamflows on the Gallatin River drop throughout July, trout will follow the hatches. Unlike June when most of the trout are found near bank-side structure July trout are found throughout a variety of habitats. After Golden stoneflies wane in early July, hatches of PMDs and caddis provide the bulk of a trout’s diet in July. These hatches paired with streamflows being lower than earlier in the month, cause Gallatin River trout to migrate to various feeding and holding lies in riffle corners, shelfs, drop-offs, and pocket water. 

The Gallatin River has an abundance of aquatic insect life. Because food is prevalent in many habitats, trout inhabit many places, but they are most often found along the bank, in riffles, shelfs, the heads of runs, and the tail outs of runs. These habitats all offer the primary needs for trout: available food source, cover from predators, cover from strong currents, and flowing water for oxygen. 

In July on the Gallatin River, anglers typically rejoice because the trout tend to be hungry and happy and in the right spots.

Important July hatches

If salmonflies are the star of the show in June on the Gallatin River, July features an ensemble cast. Most stoneflies—Golden stoneflies and Yellow Sally stoneflies—are finished hatching on the Gallatin River by the second week of July. 

After these stoneflies hatch, hatches of caddis and Pale Morning Dun (PMD) mayflies are strong. Stoneflies, caddis, and PMDs can hatch at subsequent times as well. A variety of caddis species ranging in size from 10 to 20 live in the Gallatin River and hatch throughout the month, occurring at various times throughout the day. 

PMD hatches typically begin mid-morning and last for several hours. Insects range in sizes from 12 to 18, with most being size 16. As a mayfly, it is important to understand trout may feed on emerging PMDs and not exclusively on fully hatched adults. 

Grasshoppers, although not an aquatic insect, can be found on bankside grasses in late July. Opportunistic trout will eat a grasshopper that has mistakenly found its way onto the water. 

By the last week of July trico mayflies may hatch on the Gallatin River. These small black-bodied and white-winged mayflies are tiny, ranging in size from 18 to 22. Tricos are a hatch best reserved for anglers desiring small-fly, sight-fishing opportunities. 

Gallatin River fly box for July

Stonefly nymphs in brown and black in sizes 4 to 10

Golden stonefly dry flies in sizes 8 and 10

Yellow Sally nymphs in sizes 10 to 16

Yellow Sally dry flies in sizes 10 to 16

PMD nymphs sizes 12 to 18

PMD emergers sizes 12 to 18

PMD dry flies sizes 12 to 16

Caddis pupae sizes 12 to 16

Caddis CDC emergers sizes 12 to 16

Caddis dry flies with dark grey, black or brown bodies in sizes 12 to 18; 

Grasshoppers in sizes 4 to 12

Ants and beetles in sizes 12 to 18

Trico nymphs size 18 to 22

Trico emergers sizes 18 to 22

Trico dry flies sizes 18 to 22

Crayfish patterns in sizes 2 to 8

Sculpin patterns in sizes 2 to 6

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