Boulder River Fly Fishing in August

Boulder River Fly Fishing in August

Irrigation demands, coupled with the depletion of snow in the high country quickly dewaters the Boulder River by late July. August and September are low-water months for the Boulder River, making float fishing all but impossible. Warm air temperatures and low flows create warm water temperatures, making morning fishing ideal in August.

Boulder River Fly Fishing Hatches in August

Sporadic and sparse hatches in August cause the Boulder River trout to tune their full attention to terrestrial insects. Grasshopper, beetles, ants, and Spruce Moth patterns are the mainstays of the trout diet in August.

Spruce Moth activity varies year to year on the Boulder River, but be quick to switch to a light-colored fly like a tan Elk Hair Caddis in sizes 14-16 if you see them around on rocks or flying above the water’s surface. They can be of particular importance on the upper river stretches in mid-August.


Boulder River Fly Box in August


Boulder River Fly Fishing Techniques in August

Low flows and clear water create a much more technical Montana fly fishing scenario than a Boulder River angler would encounter in June or July. Small attractor dry flies like the Purple Haze, Royal Para-Wulff, or H&L Variant in sizes 14-16 are standard offerings. Use long leaders with 5X or 6X tippet as the sun climbs into the summer sky as trout become wary during low flows.

Dry dropper rigs with Chubby Chernobyl dries in size 10-14 followed by small, weighted nymphs are effective in the faster runs below riffles and seams alongside boulders.

Bozeman Fly Fishing Guide Pro Tip:

Walking in above the Natural Bridge Falls picnic area is a great way to find cruising Rainbow and Cutthroat Trout in gin-clear water. Try spotting cruising fish from the elevated banks and target them with a dry dropper rig in the slow-moving current.

A Parachute Hopper with a Black Micro Mayfly nymph is size 18 will do the trick, most days. Place the flies 10-20 feet ahead of the cruising trout and give the flies a subtle “twitch” when the fish is a few feet away.

Boulder River Fly Fishing Trips in August

Warm water and low flows make Boulder River fishing trips a low priority for our Bozeman fly fishing guides in August. The Yellowstone, Madison, and Gallatin Rivers are more reliable options than most of the small rivers and streams in Montana during August and September.

Boulder River excursions in August are well suited to advanced anglers who are physically fit and willing to walk several miles along the slippery river bottom. Angling pressure is light, however, water temperatures and flows make for challenging conditions.

Fins and Feathers Guide Service has been outfitting flyfishing Montana trips for over two decades. Our guests have come to rely on our expertise when asking for day trip recommendations and the Boulder River is rarely counted on in August.

Fly fishing trips near Bozeman, Montana with our team of Montana fishing guides can be secured online, via e-mail, or by calling us at 1-406-468-5019. Contact us for more information about our Boulder River fishing trips near Big Timber.

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