By late July most Western freestones have dropped and warmed to the point where the trout eat hard for two short windows a day and sulk through the rest of it. The summer angler's job is to be on the water for those windows, to know when the water is too warm to fish at all, and to carry the two fly boxes that matter in July and August: terrestrials and Tricos. The June hatches are on their own page; this one starts when they fade.
The early and late windows
Summer fishing is bookended. The first window opens at first light and closes when the sun hits the water and the temperature starts climbing, and it belongs to Trico spinners and PMD leftovers. The second opens when the sun leaves the water in the evening and runs to dark, and it belongs to caddis, PMD spinner falls, and, on a lot of rivers, the biggest fish of the day. The middle of the day is hopper time along shaded banks and undercut grass, but only as long as the water stays cool enough.
Plan your day around those windows rather than around a normal schedule. On the water at dawn, off by late morning, back at six. If you can only fish one, fish the evening; the water is at its warmest but the fish have had all day to get hungry and the light is on your side.
Water temperature: when to stop
Trout are cold-water fish, and warm water carries less oxygen at the same time it raises their metabolism. A fish fought in warm water may swim away and die an hour later. Carry a thermometer and use it, because this is the one decision in summer that is about the fish rather than about you.
The number most anglers, guides, and agencies use is a water temperature in the upper 60s Fahrenheit as the point to stop fishing for trout; many treat 68 degrees as the line. Below that, fight fish fast, keep them in the water, and skip the photo. At or above it, reel up. Fish are in trouble before they look like it. In hot summers Montana Fish, Wildlife and Parks and other state agencies issue afternoon closures (often called hoot-owl restrictions) on specific rivers; those change year to year and river to river, so check the agency before you go rather than relying on last year's list.
When your home freestone is too warm, the fish-friendly moves are the tailwaters, which run cold all summer below the dam, and the high-elevation streams. Both are covered below.
Terrestrials: hoppers, ants, and beetles
Grasshoppers are marked at peak in July and August on 37 rivers here, nearly all freestones with grassy banks. In Montana that is the Madison, Yellowstone, Big Hole, Bitterroot, Blackfoot, Clark Fork, Gallatin, and Rock Creek. In Idaho and Wyoming the South Fork, Snake, New Fork, North Platte, Salmon, and Lochsa, plus the Lamar and Firehole in the park. In Colorado the Colorado, Roaring Fork, and Poudre; in Utah the Bear, Duchesne, Fremont, Price, Sevier, and Uinta; in New Mexico the Pecos, Red, and Rio Grande. The Green below Flaming Gorge carries a general terrestrials row at peak in July and August.
Fish hoppers in the afternoon along grass banks, in sizes 8 to 12, with a little splat on the landing. A Chubby Chernobyl, Morrish Hopper, or Parachute Hopper, with a beadhead nymph dropped 18 inches below it. Ants and beetles, size 14 to 18, are the quieter half of the terrestrial box and often outfish the hopper on pressured water and on windy afternoons. The hopper guide and the flying ant guide go deeper.
Tricos: the morning spinner fall
Tricorythodes, the Trico, is a tiny mayfly (size 20 to 24) whose spinners fall in dense clouds at sunrise, and on the rivers that have it the morning window is about nothing else. The charts mark Tricos at peak in July and August on the Bighorn, Missouri, Frying Pan, Blue, Taylor, Gunnison, South Platte, Arkansas, Boise, Silver Creek, Teton, Hat Creek, Owens, both Provos, the San Juan, and the Yakima. The Henry's Fork and Madison come on in July and peak in August.
Be there before the spinners fall, find a pod of fish on a flat, and fish a size 22 Trico spinner on 6X with a downstream reach cast. Two spinners a foot apart help you see the take. When the fish are on the duns earlier, a size 22 black-bodied parachute. The Trico guide has the details.
PMDs and Golden Stones on the freestones
The mayfly and stonefly hatches that the tailwaters got in June arrive on the freestones in July once the water drops. PMDs are marked at peak in July on 76 rivers and Golden Stones on 64, including nearly every Montana, Idaho, and Wyoming freestone. Fish the PMDs in the late morning window and the Golden Stones as a size 8 to 10 foam adult through midday and evening, with a Pheasant Tail or a golden stone nymph as the dropper under either.
High-elevation and tailwater escapes
When the valley rivers are too warm by noon, go up or go below a dam. The Uinta Mountain freestones in Utah, the Uinta, Lake Fork, and the brook-trout headwaters of the Upper Provo, run cold through August and their hatch rows (Golden Stone, caddis, PMD, hopper) all sit at peak in July and August. The Yellowstone park rivers are the same story. On the tailwaters, the water leaving the dam is cold regardless of the air temperature, and the Trico and PMD rows above are almost all tailwater rivers for that reason.
The summer kit
- A stream thermometer, checked at the start and again at midday.
- Hoppers 8 to 12, ants and beetles 14 to 18, a few Chubbies for the Golden Stones.
- Trico spinners 20 to 24, PMD duns and spinners 16 to 18, and a spool of 6X.
- Evening caddis: Elk Hair Caddis and X-Caddis 14 to 16.
- Water, sun protection, and a plan to be off the water by late morning on the warm freestones.