South Fork
SOUTH FORK
ReportAUG 4 — 11, 2026
🌊
Flow
12200 CFS
SNAKE RIVER NR IRWIN ID
🌡️
Water Temp
48.9°F
Updated 2026-08-04
☀️
Weather
51–85°F
Patchy Smoke
🎣
Reported By
Bruce Staples
On the water
The Big Rock Fire has closed all BLM access from Conant to Byington through August 10th, pushing angling pressure to the Palisades Dam–Spring Creek corridor and the lower river. Flows are elevated — 12,200 cfs at Irwin, 10,200 cfs at Heise, and roughly 5,100 cfs at Lorenzo — as river water is being drawn to fight the fire, with water temps running a cold 48.9°F.
From the ShopBruce Staples · August 4, 2026
The Big Rock Fire has prompted BLM and other agencies to close all activities on and along the South Fork from Conant to Byington through August 10th. Included are all boat launch sites, all riverside campsites, trails, and streamside roads.
Look for increased boating use of the river from Palisades Dam downstream to Spring Creek and on the lower river. Changes in flow below the dam are 12,200 cfs at Irwin, 10,200 cfs at Heise, and about 5,100 cfs at Lorenzo. River water is being used to fight the fire.
What's Working — Hot Flies
Hatch Chart
| Insect | Size | Activity | Prime Time |
|---|---|---|---|
| Grasshoppers / Terrestrials | #6–#12 | Seasonal — August prime time | Midday–Afternoon |
| Caddis | #16–#20 | Seasonal — August evenings | Evening |
| PMD | #16–#20 | Seasonal — August mornings | Morning |
| Baetis / BWO | #20–#22 | Seasonal — overcast or smoky conditions | Morning–Afternoon |
Best Time Window
- THROUGH AUG 10: Avoid the Conant-to-Byington corridor entirely — all access points, launches, and streamside roads are closed due to the Big Rock Fire.
- PALISADES DAM TO SPRING CREEK: The open upper reach is fishable but expect elevated flows (9,350 cfs at Irwin) and increased boat traffic — focus on inside seams and slower water.
- LOWER RIVER: The lower South Fork below the closure zone is also open — morning and evening sessions will be most comfortable given afternoon smoke and heat near 82–85°F.
Guide's Tip
From the benchThe field report this week is an access and safety alert, not a fishing report — Madison was not on the water fishing, so no specific fly or tactic recommendations come from the South Fork this week. Check back after August 10th when the Conant-to-Byington closure lifts. In the meantime, the open stretch from Palisades Dam to Spring Creek will see heavier boat traffic, so plan accordingly and give other anglers extra room.
Main Species
Yellowstone Cutthroat Trout
Brown Trout
Rainbow Trout
