Northern Rockies
Montana FWP's salmonfly, caddis and Trico timing, and the season dates set by Yellowstone and Grand Teton national parks and Idaho. Each row is charted only for the months its source gives; where a source names an insect but gives no months, it is not charted. Conditions vary by water and year: use this to plan, then ask a local shop.
- 8sourced rows
- 5sources
- 3states
Month by month
- Hatch
- Season or closure
| Event, where, source | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Mother's Day caddis (Grannom)Hatch · Big Hole River, Montana[1] Montana Fish, Wildlife & Parks | January: no | February: no | March: no | April: no | May: yes | June: no | July: no | August: no | September: no | October: no | November: no | December: no |
| SalmonflyHatch · Big Hole River, Montana[1] Montana Fish, Wildlife & Parks | January: no | February: no | March: no | April: no | May: yes | June: yes | July: no | August: no | September: no | October: no | November: no | December: no |
| SalmonflyHatch · Montana salmonfly rivers (statewide overview)[2] Montana Fish, Wildlife & Parks | January: no | February: no | March: no | April: no | May: yes | June: yes | July: yes | August: no | September: no | October: no | November: no | December: no |
| SalmonflyHatch · Madison River above Ennis, Montana[2] Montana Fish, Wildlife & Parks | January: no | February: no | March: no | April: no | May: no | June: no | July: yes | August: no | September: no | October: no | November: no | December: no |
| TricoHatch · Big Hole River, Montana[1] Montana Fish, Wildlife & Parks | January: no | February: no | March: no | April: no | May: no | June: no | July: no | August: yes | September: yes | October: no | November: no | December: no |
| General fishing seasonSeason or closure · Yellowstone National Park (most waters)[3] National Park Service (Yellowstone National Park) | January: no | February: no | March: no | April: no | May: yes | June: yes | July: yes | August: yes | September: yes | October: yes | November: no | December: no |
| Snake River cutthroat catch-and-release periodSeason or closure · Snake River, Grand Teton National Park, Wyoming[4] National Park Service (Grand Teton National Park) | January: yes | February: yes | March: yes | April: no | May: no | June: no | July: no | August: no | September: no | October: no | November: yes | December: yes |
| Harriman Ranch section closed to fishingSeason or closure · Henrys Fork, Harriman State Park (Harriman Ranch), Idaho[5] Idaho Department of Fish and Game | January: yes | February: yes | March: yes | April: yes | May: yes | June: yes | July: no | August: no | September: no | October: no | November: no | December: yes |
- Mother's Day caddis (Grannom) MayHatch · Big Hole River, Montana · [1] Montana Fish, Wildlife & Parks
- Salmonfly May to JuneHatch · Big Hole River, Montana · [1] Montana Fish, Wildlife & Parks
- Salmonfly May to JulyHatch · Montana salmonfly rivers (statewide overview) · [2] Montana Fish, Wildlife & Parks
- Salmonfly JulyHatch · Madison River above Ennis, Montana · [2] Montana Fish, Wildlife & Parks
- Trico August to SeptemberHatch · Big Hole River, Montana · [1] Montana Fish, Wildlife & Parks
- General fishing season May to OctoberSeason or closure · Yellowstone National Park (most waters) · [3] National Park Service (Yellowstone National Park)
- Snake River cutthroat catch-and-release period November to MarchSeason or closure · Snake River, Grand Teton National Park, Wyoming · [4] National Park Service (Grand Teton National Park)
- Harriman Ranch section closed to fishing December to JuneSeason or closure · Henrys Fork, Harriman State Park (Harriman Ranch), Idaho · [5] Idaho Department of Fish and Game
What each source says
The source's own words behind every row, so you can see exactly where the months come from.
- Mother's Day caddis (Grannom), Big Hole River, Montana (May):
The Mother's Day caddis hatch happens in early May, when size 14 Grannom caddis start coming off.
[1] - Salmonfly, Big Hole River, Montana (May to June):
That famous salmonfly action starts in late May or early June on the lower river and works its way up to Fish Trap Fishing Access Site above Wise River by late June.
[1] - Salmonfly, Montana salmonfly rivers (statewide overview) (May to July):
When to fish: The hatch runs from mid-May to early July, depending on the river and stretch.
[2] - Salmonfly, Madison River above Ennis, Montana (July):
The Madison's salmonfly hatch is popular and attracts anglers from throughout the United States. Salmonflies begin emerging around July 1 in the channels just above Ennis, and the hatch moves upstream several miles per day over the next three weeks.
[2] - Trico, Big Hole River, Montana (August to September):
The tiny black-bodied Trico mayflies start coming off in mid-August and last through mid-September.
[1] - General fishing season, Yellowstone National Park (most waters) (May to October):
Most waters are open to fishing from the Saturday of Memorial Day weekend (usually the last weekend in May) through October 31.
[3] - Snake River cutthroat catch-and-release period, Snake River, Grand Teton National Park, Wyoming (November to March):
Rivers and Streams: All cutthroat trout caught in the Snake River must be released to the water immediately from November 1-March 31.
[4] - Harriman Ranch section closed to fishing, Henrys Fork, Harriman State Park (Harriman Ranch), Idaho (December to June):
Section: From the lower Harriman State Park boundary upstream to the upper Harriman State Park boundary (Harriman Ranch) • December 1 through June 14 – closed to fishing
[5]
Use it on the water
Pick flies with the fly finder, check an insect with the fly identifier, and read the flow and temperature on each water page before you go.
- Montana watersWater pages
- Wyoming watersWater pages
- Idaho watersWater pages
Sources
Every fact on this page is our paraphrase of the page cited beside it, read on the date shown. Rules and seasons change: check the agency's current regulations before you fish.
- Montana Outdoors, May-June 2020: Big Hole (Fishing the Big Hole through the Year) Montana Fish, Wildlife & Parks, read Oct 24, 2026.
- Montana Outdoors, May-June 2011: Salmonflies Montana Fish, Wildlife & Parks, read Oct 24, 2026.
- Yellowstone National Park - Fishing Regulations 2026 National Park Service (Yellowstone National Park), read Oct 24, 2026.
- Fishing - Grand Teton National Park National Park Service (Grand Teton National Park), read Oct 24, 2026.
- Idaho Fishing 2025-2027 Seasons & Rules (2nd Edition 2026) Idaho Department of Fish and Game, read Oct 24, 2026.
Other regions
- Pacific Northwest10 rows
- California19 rows
- Southwest and Colorado8 rows
- Alaska8 rows
- Driftless19 rows
- Catskills and the Northeast17 rows
- Southern Appalachians27 rows
- Ozarks3 rows
- Great Lakes10 rows