July Fishing on the Missouri River

July weather, streamflow's, and summary

The Missouri River in July is a dry fly anglers dream stream. From hatches of Pale Morning Duns and caddis early in the month to grasshoppers and the oh-so-technical trico mayflies, mid-summer on the Missouri River brings consistent hatches matched with consistent streamflows. July is when the Missouri River shows all its cards and it is often a full house. 

As streamflows stabilize in early July, floating and wading anglers enjoy a river in ideal conditions. The entire river, including The Land of Giants below Hauser Dam, all the way down to Cascade can experience strong hatches and actively feeding trout every day of the month. With an abundance of hatches, days filled with sunshine, and streamflows at very friendly floating and wading levels the Missouri River in July has something for everyone. 

Snowmelt runoff is complete so rising flows are in the past. Additionally, because the Missouri River flows are regulated by several reservoirs, streamflows in July remain relatively consistent throughout the month. These stable streamflows create a fishery that acts more like a spring creek than a typical mountain river. Dry fly fishing is the desired method during July, because the Missouri River is filled with a variety of aquatic insects that are active year-round, July is not reserved only for dry fly anglers. Anglers wanting to fish tandem two-fly nymph rigs or swinging flies or spey casting can have success.

July weather on the Missouri River is pleasant. Ideally suited for the sun shirt and flip-flop crowd and wet-wading, daytime highs average in the 80 degrees F throughout the month. With an average monthly precipitation less than 0.9 inches of rain, July is usually sunny and dry. Towards the end of July the prolonged days of sunshine and warm temperatures can create rising water temperatures, however because the Missouri River’s streamflows originate from bottom-release dams, water temperatures in July are almost always trout friendly. 

July fishing: what to expect

Early July on the Missouri River sees strong hatches of Pale Morning Duns (PMDs) and caddis. The stable streamflows of early July translate into actively feeding trout. Stable streamflows—typically between 3,500 and 6,500 cubic feet per second—are common during the first two weeks of July. Later in July streamflows may decrease slightly from their early July levels, but the decrease in flows is usually minimal and proportionate to the starting level. 

With these stable flows PMDs, caddis, and trico mayflies are the primary food source for trout on the Missouri River for most of July. With a strong emergence of both species, expect fish to actively feed on emerging and adult PMDs and caddis. PMD dry flies and emergers in sizes 14 through 18 fished in riffles and shallow flats are preferred and caddis dry flies and emergers in sizes 14 through 16 fished in similar habitats should entice fish. Trico mayflies are very small—size 18 to 22—and serve up a unique style of dry fly fishing for skilled anglers. 

A highlight of fishing the Missouri River in July is sight-fishing to “pods” of feeding trout. Because several thousand insects may hatch in a given area, the Missouri River’s trout will group together and feed on hatching insects. These pods of fish may be feeding on emerging insects or fully hatched surface-floating insects. Determining whether a fish is picking-off emerging insects or fully hatched adults is easy. As the fish is rising, if they rise in a head-first, tail-second rhythm, they are eating insects that are emerging slightly before they hatch into adults. If a trout is rising in a mouth-first, mouth-open rhythm, then they are eating fully hatched adults. 

A proven tactic on the Missouri River when fishing to a pod of fish is to fish two flies. Choose a floating dry fly—one that imitates a fully hatch adult insect—and a second fly that imitates an emerging insect. For mayflies, popular combinations are a Sparkle Dun and an RS2. For caddis, a good go-to setup is an Elk Hair caddis and a Sparkle Pupa. 

Grasshoppers, ants, beetles, crickets, and other land-based terrestrial insects are prevalent in July on the Missouri River. As the month progresses and hatches of PMDs and caddis slowly taper, trout are still actively feeding and a floating grasshopper, ant, or beetle may get gobbled.

Two-fly tandem nymph rigs also work well on the Missouri River in July. With hatches strong and water temperatures in the high 50s to mid-60 degrees F, trout will actively seek out food. Weighted two-fly rigs with Pheasant tails, caddis pupae, scuds, sow bugs, or midge patterns can quickly rack up the number of fish to the net. 

Recently, anglers have begun to spey cast and swing flies in many of the Missouri River’s productive riffles and runs. With streamflows conducive to wading, July is a fine time to spey cast and swing flies on the Missouri River. 

Where to find July trout on the Missouri River

July on the Missouri River typically sees streamflows in the range of 3,000 to 6,000 cubic feet per second. Compared to other rivers in Montana, this is a large volume of water. However, the Missouri River occupies a large valley floor and its habitat consists of braids, island channels, and shallow flats. 

Pale Morning Duns (PMDs) hatch in July on the Missouri River. These hatches can be very strong and many of the river’s trout will move to shallow flats, riffles, and runs, to feed on emerging nymphs or floating adults. Look for trout in faster currents along riffle corners and seams, medium-speed currents on shallow flats or long runs. As the hatch diminishes later in the day look for eddys where PMD adults may have stacked-up.

Caddis are very common on the Missouri River. During a caddis hatch, look for trout in fast, shallow areas of the river. Target water with a stream bottom made of small rocks or pebbles or seams along many of the large cliffs and rock shelves that protrude into the water.

When hatches of PMDs and caddis are thick, look for Missouri River trout to group up in “pods” in the various feeding lies. A well-presented fly through one of these pods may entice a strike.

Terrestrials—grasshoppers, ants, beetles, crickets, and any other insect that may find itself in the water—make up a sizable portion of a Missouri River trout’s diet in July. When fishing a terrestrial, focus on all possible feeding lies—near bankside structure, seam lines between slow and fast water, currents flowing along the limestone canyon walls, shallow flats, riffle corners, and the heads of deep pools.

Important July hatches

Hatches of Pale Morning Duns (PMDs), caddis, and trico mayflies occur in July. PMDs and caddis are the primary hatches on the Missouri River in July. With the Missouri River’s abundance of long riffles and shallow flats and a streambed of cobble-sized rocks and weed humps, the river is home to ideal habitat for PMDs and caddis. 

Emerging out of riffles and flats, PMDs mayflies create ample opportunities for floating and wading anglers. Caddis hatches can last throughout the month. Emergences can be very strong and with dozens of species of caddis in the Missouri River, trout have plenty of insects from which to choose. Most caddis on the Missouri River are sizes 14 through 18 and most PMDs are sizes 14 through 18 as well. 

The numerous riffles and shallow flats on the Missouri River around Craig experience world-renown hatches of PMDs and caddis in July. 

Trico mayflies hatch in the early morning hours. Trout rarely feed on trico nymphs but will often rise to adults floating on the surface or “spent” adults—insects that have mated and are now dead. 

Terrestrials—insects that live the entirety of their life on land—provide a large portion of a Missouri River trout’s diet in late July. Grasshoppers, crickets, ants, beetles, spiders, and any other land-dwelling insect that may inadvertently find its way onto the surface will be targeted by trout as well. 

Missouri River fly box for July

Caddis pupae size 14 to 18

Caddis CDC emergers size 14 to 18

Caddis dry flies with dark grey, black or brown bodies in size 14 to 18; 

PMD dry flies size 14 to 20

PMD emergers size 14 to 20

PMD nymphs size 14 to 20

Trico nymphs in sizes 18 to 22

Trico duns/adults in sizes 18 to 22

Trico spinners in sizes 18 to 22

Grasshoppers, in tan or peacock, in sizes 4 to 14

Ants and beetles in sizes 12 to 18

Scuds in sizes 10 through 20

Sowbugs in sizes 10 through 20

Midges, especially Zebra midges in black and olive, in sizes 16 through 22

Sculpin patterns in sizes 2 to 6

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