Idaho has two rivers that anglers everywhere know by their first names, Henry's Fork and Silver Creek, and both are spring creeks in a state that is otherwise mountains, canyons and freestone. That contrast is Idaho: the most technical dry-fly water in the country sits in the same state as the Lochsa and the Selway, where westslope cutthroat rise to a #10 Stimulator without hesitation. Idaho also has the only inland steelhead fishing in this group of states, with fish that swim from the Pacific to Riggins, Orofino and Stanley. Runoff runs from May into early July on the freestones, and the spring creeks and tailwaters carry the early season.
Henry's Fork: Box Canyon, Last Chance and Harriman
The Henry's Fork below Island Park Dam is three rivers in a few miles. Box Canyon is fast pocket water where big rainbows eat Salmonflies in late May and June and heavy stonefly nymphs the rest of the year. Last Chance and Harriman State Park downstream are slow, flat spring-creek water where the hatches stack up: Pale Morning Duns from May into August, Green Drakes in June and July, Callibaetis from the lake outflow through summer, and Tricos into September. This is CDC Baetis Emergers and Vis-A-Duns in #18 to #20, long leaders and drag-free drifts to fish that refuse anything less. Flows of 400 to 2,000 cfs on gauge 13037500 are the fishing range. Henry's Lake above it is one of the best trophy stillwaters in the West.
The South Fork of the Snake and the Teton
The South Fork of the Snake below Palisades Dam is Idaho's great float river: canyon and cottonwood bottoms from Swan Valley to Lorenzo, with Snake River fine-spotted cutthroat, browns and rainbows. The Salmonfly hatch in June and July, Golden Stones through July, and grasshoppers from July into September make it a big-dry-fly river; Chubby Chernobyls and Sofa Pillows in #4 to #6 are standard. It is a large river, with flows from 3,000 to 20,000 cfs, and most of it is fished from a boat. The Teton River in the valley between Driggs and Tetonia is the opposite: a slow, technical freestone with Pale Morning Duns and Tricos, best fished quietly in June, July and September.
South-central and southwest Idaho: Silver Creek, the Big Wood and the Boise
Silver Creek and the Big Wood
Silver Creek near Picabo is the spring creek Hemingway fished, now anchored by the Nature Conservancy Preserve. Pale Morning Duns, Callibaetis, Tricos and damselflies run from June into September, and the brown drake emergence in early June is the hatch people time trips around. Flies are #18 to #22 with CDC, and the fish are as selective as any in the state. The Big Wood River through Ketchum and Hailey is the valley's freestone, fishing well with Pale Morning Duns and Golden Stones from late June and hoppers through September. The Little Wood, gauged, is the smaller sibling without a page yet.
Steelhead: the Clearwater and the Salmon
The Clearwater River at Orofino is famous for B-run steelhead, the large, late-returning fish that arrive from September through November and hold through the winter. The lower canyon around Orofino and the Dworshak Dam reach at Ahsahka are the core water, swung with Intruders and traditional patterns on Spey rods. The Salmon River, the River of No Return, carries steelhead far into central Idaho, and the reach from Riggins up to North Fork fishes for them in fall and again in spring. Steelhead seasons and bag limits in Idaho depend on annual run forecasts and change quickly; do not plan a trip without checking Idaho Fish and Game first.
Panhandle cutthroat: the St. Joe, the Lochsa and the Selway
Northern Idaho's rivers are westslope cutthroat water, and the fishing is about as simple and satisfying as trout fishing gets. The St. Joe River above Avery is a cutthroat river long managed for catch-and-release, with Salmonflies in June, Golden Stones through July and caddis all summer. The Lochsa along US-12 is a big, clear canyon river with the same cutthroat and the same stoneflies, fishable once runoff drops in July. The Selway, the Coeur d'Alene and its North Fork, the Moyie and the Kootenai are all gauged and unwritten here. Lake Pend Oreille, the huge lake at Sandpoint, is known for large rainbows and lake trout.
The Boise and the southwest
The Boise River below Diversion Dam runs through the capital's Greenbelt as an urban tailwater with browns and rainbows, a Mother's Day caddis hatch in April and May, and Tricos in late summer. The South Fork Boise below Anderson Ranch Dam, gauged with temperature, is the bigger and better-known tailwater and does not have a page yet; the Payette forks and the Bruneau and Owyhee canyon rivers are gauged desert and mountain water for future coverage. Redfish Lake sits under the Sawtooths near Stanley.
Before you go
Idaho Fish and Game sets steelhead seasons in-season based on returns, and several rivers, including Silver Creek and the St. Joe, carry special regulations. Check the agency before every trip, not just the first one. Flows on Henry's Fork and the South Fork are dam releases and can change on an irrigation schedule. See the Idaho fishing hub for all gauged waters in the state and the Idaho trout page for trout detail.