Mayflies
Caddisflies
The water through Yellow River State Forest is among Iowa's premier trout fishing — wild browns in a big block of protected hardwood-forest backcountry, with camping and trails. The most wilderness-feeling fishing in the state.
- Limestone
Rules at a glance
- Free fishing
Water temperature for Brown Trout
Warm — slow17°C est.ideal 10–16°C
0°14°28°
How to fish it · for Brown Trout
When
Nymphing can work through most of the day.
Where
Cover mixed depths.
Method
Start with tight-line nymphs and adjust if fish rise or drift higher.
Kit
9 ft #4 rod, floating line, 12 ft tapered leader to 4–5 lb fluoro tippet.
Why this works
Water at 20°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Likely species
Mayflies
Caddisflies
Hatch timeline · tomorrowPeak at 7am
12pm(now) — Reed Smut
Stage: On emergersApproach: Emerger or dryActivity: 59%
Also:Flying Ants55%Trico (Eastern)44%
Peak emergence window5 food groups active
Peak activity at 7am — Trico (Eastern) (Trico (Eastern), Degree-days at peak)
Sub-surface · on the nymphunder the surface
Hatch predictions
See the full sub-surface read with Pro.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey(1)
Hatch predictions
Top prey shown — see all 4 with Pro.
Start free trial14-day free trial. Cancel anytime.
Evidence
Records-basedModerate confidence
Based on species-occurrence records, not local invertebrate surveys.
Through the year
0–3 scale · September highlighted
J
F
M
A
M
J
J
A
S
O
N
D
SulphurHatch
2
3
2
Trico (Eastern)Hatch
2
3
3
2
Eastern Blue-Winged OliveHatch
2
3
3
3
3
3
3
3
2
Eastern Summer BWO (Drunella)Hatch
2
3
3
2
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Brown Trout fly box
Local fly shops: Driftless Fly Fishing Co.
Permits & access
Permit required — see local rules.
- Iowa DNR — state forest; verify regulations.
What's coming
Plan ahead
5-day outlook
Water here at 20.0°C. Nothing cooler within range.
Gallery · 1
Terrain map
About this water
Water quality · US Clean Water Act
- Aquatic life: Impaired
What this classification means
EPA ATTAINS assessment unit 'Yellow River' (IA 01-YEL-435), 2024 Integrated Report. Aquatic Life use: Not Supporting. Listed impairment causes: Cause Unknown Impaired Biota. This is a Clean Water Act assessment-unit classification (the US analogue of WFD), not a live reading.
Status is for the Clean Water Act assessment unit covering this reach.
EPA ATTAINS (Clean Water Act) · IA 01-YEL-435
The full read · show the working · for Brown Trout · confidence 80%
How the 26 is built — score × weight = contribution
Temperature13 × 28%3.6
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time65 × 13%8.5
Pressure80 × 7%5.6
Insect activity57 × 12%6.8
Limiting factor: Water temperature (20°C) is outside Brown Trout's preferred range (10–16°C)= 59
Can you trust it?
Water temperaturelive gauge readinggauge
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
Cooler water — back toward the 10–16 °C ideal band — would lift the score and ease welfare.
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
- Trout Open all year → Open all year
Related guides
Booking & contacts
Yellow River
The water through Yellow River State Forest is among Iowa's premier trout fishing — wild browns in a big block of protected hardwood-forest backcountry, with camping and trails.
Water temperature for Brown Trout
Warm — slow17°C est.ideal 10–16°C
0°14°28°
How to fish it · for Brown Trout
When
Nymphing can work through most of the day.
Where
Cover mixed depths.
Method
Start with tight-line nymphs and adjust if fish rise or drift higher.
Kit
9 ft #4 rod, floating line, 12 ft tapered leader to 4–5 lb fluoro tippet.
Why this works
Water at 20°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Likely species
Mayflies
Caddisflies
Hatch timeline · tomorrowPeak at 7am
12pm(now) — Reed Smut
Stage: On emergersApproach: Emerger or dryActivity: 59%
Also:Flying Ants55%Trico (Eastern)44%
Peak emergence window5 food groups active
Peak activity at 7am — Trico (Eastern) (Trico (Eastern), Degree-days at peak)
Sub-surface · on the nymphunder the surface
Hatch predictions
See the full sub-surface read with Pro.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey(1)
Hatch predictions
Top prey shown — see all 4 with Pro.
Start free trial14-day free trial. Cancel anytime.
Evidence
Records-basedModerate confidence
Based on species-occurrence records, not local invertebrate surveys.
Through the year
0–3 scale · September highlighted
J
F
M
A
M
J
J
A
S
O
N
D
SulphurHatch
2
3
2
Trico (Eastern)Hatch
2
3
3
2
Eastern Blue-Winged OliveHatch
2
3
3
3
3
3
3
3
2
Eastern Summer BWO (Drunella)Hatch
2
3
3
2
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Brown Trout fly box
Local fly shops: Driftless Fly Fishing Co.
Permits & access
Permit required — see local rules.
- Iowa DNR — state forest; verify regulations.
What's coming
Plan ahead
5-day outlook
Water here at 20.0°C. Nothing cooler within range.
Gallery · 1
Terrain map
About this water
The water through Yellow River State Forest is among Iowa's premier trout fishing — wild browns in a big block of protected hardwood-forest backcountry, with camping and trails. The most wilderness-feeling fishing in the state.
- Limestone
Water quality · US Clean Water Act
- Aquatic life: Impaired
What this classification means
EPA ATTAINS assessment unit 'Yellow River' (IA 01-YEL-435), 2024 Integrated Report. Aquatic Life use: Not Supporting. Listed impairment causes: Cause Unknown Impaired Biota. This is a Clean Water Act assessment-unit classification (the US analogue of WFD), not a live reading.
Status is for the Clean Water Act assessment unit covering this reach.
EPA ATTAINS (Clean Water Act) · IA 01-YEL-435
The full read · show the working · for Brown Trout · confidence 80%
How the 26 is built — score × weight = contribution
Temperature13 × 28%3.6
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time65 × 13%8.5
Pressure80 × 7%5.6
Insect activity57 × 12%6.8
Limiting factor: Water temperature (20°C) is outside Brown Trout's preferred range (10–16°C)= 59
Can you trust it?
Water temperaturelive gauge readinggauge
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
Cooler water — back toward the 10–16 °C ideal band — would lift the score and ease welfare.
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
- Trout Open all year → Open all year
Related guides
Booking & contacts