Williamson River
Klamath Marsh to Agency Lake
S Oregon, USA
Open live forecast →Target species: Rainbow and Brown.
Stream gauge: 11499100. Flow and water temperature update on every refresh.
Weekly AI Outlook as of 06/05/26
June on the Williamson means one thing: hexagenia season is here. These massive mayflies (#4-8) emerge during evening hours and draw the basin's famous 20+ inch rainbows to the surface. Water temps are settling into the mid-to-upper 50s, perfect for triggering consistent emergence. PMDs are also active during afternoon hours as a reliable backup. Fish subsurface with weighted nymphs during the day, then switch to large hex dries at dusk. The cooling trend midweek won't shut down evening emergence but may push prime time slightly later.
- Conditions: Spring-fed consistency with water temps climbing into the ideal 54-58°F range for peak hexagenia emergence activity
- Hatches: Hexagenia mayflies (#4-8) emerging at dusk — the premier Oregon hatch. PMDs active during warmer afternoon hours
- Water Temp: Mid-to-upper 50s — crossing into prime hex territory with evening emergence windows extending as temps stabilize
- Best Window: Evenings from 7-9pm for surface action. Midday nymphing productive before the evening show begins
Generated weekly from live USGS gauge readings, weather forecasts, and recent fly shop reports. Updates Friday mornings.
About this Water
- Spring Creek
- Best months: May–Oct, peak Aug–Sept
The Williamson River in south-central Oregon is one of the West's most distinctive trout fisheries — a slow, broad spring-fed river running through the Klamath Basin's high desert and supporting massive Klamath redband trout. Fish in the 5–10 pound class are routinely caught; 12+ pound fish are documented annually. The water is unusual: long, flat, weedy runs that look more like a spring creek than a Western trout river. Hatches are subtle and continuous; sight fishing to large cruising fish is the standard technique. The Williamson has a small but devoted following among trophy hunters.
The Williamson regularly produces redband trout exceeding 10 pounds — the largest documented native rainbow trout in the United States — drawn out of Klamath Lake to spawn each summer.
January Outlook
January on the Williamson is the winter off-season. The river flows from Upper Klamath Lake through the Klamath marsh and is accessible near Chiloquin and Kirk. Midges and mysis shrimp patterns produce resident rainbows in the spring-fed sections.
Productive Patterns
- Zebra Midge
- Mysis Shrimp Pattern
- RS2
- Soft Hackle
Tips
Winter on the Williamson is rarely visited but productive for those who know the spring-fed sections near Kirk. The Klamath marsh country is beautiful under winter skies. The spring-fed tributaries near the headwaters stay warmer than the main river.
Water Notes
Stable spring-fed 500–1,200 cfs. Water 46–52°F in winter. The Williamson's spring-fed character provides thermal consistency.
February Outlook
February midge and Baetis fishing on the Williamson. The river's spring-fed origin keeps temperatures above freezing and fish feeding year-round.
Productive Patterns
- Zebra Midge
- Baetis Nymph
- RS2
- Soft Hackle Emerger
Tips
The Williamson near Chiloquin is accessible year-round. February provides solitary fishing for resident rainbows with midge and early Baetis nymphs. The river's large trout population keeps the fishing worthwhile.
Water Notes
500–1,200 cfs. Water 46–52°F. Stable spring-fed flows. Good winter midge fishing.
March Outlook
March on the Williamson brings early Baetis activity and the first surface feeding of the year. The spring-fed Klamath tributary is coming alive after winter.
Productive Patterns
- Baetis Sparkle Dun
- Elk Hair Caddis (small)
- RS2
- PMD Nymph
Tips
March is when the Williamson's potential begins to reveal itself. Early Baetis hatches on warm afternoons near Chiloquin. The spring-fed sections produce consistent results as temperatures stabilize.
Water Notes
500–1,500 cfs. Water 48–54°F. Early spring activity building. Klamath Basin setting is beautiful in early spring.
April Outlook
April spring fishing on the Williamson with Callibaetis and early PMD hatches building. Large rainbow trout becoming more surface-oriented as temperatures warm.
Productive Patterns
- Callibaetis Sparkle Dun
- PMD Nymph
- Elk Hair Caddis
- Soft Hackle
Tips
April is excellent on the Williamson. The Kirk section above Upper Klamath Lake is prime for large rainbows on spring hatches. The river's spring-fed flows stay consistent regardless of Cascade snowmelt.
Water Notes
500–1,500 cfs. Water 50–58°F. Spring hatches building. The Klamath Basin setting is beautiful with meadow wildflowers.
May Outlook
May brings excellent Callibaetis and PMD hatches to the Williamson. Large rainbows become consistent risers as surface temperature warms. The famous Hexagenia season begins at month's end.
Productive Patterns
- Callibaetis Sparkle Dun
- PMD Sparkle Dun
- Elk Hair Caddis
- Hexagenia Nymph (late May)
Tips
May is excellent on the Williamson — Callibaetis and PMD action through the month with the first Hexagenia hatches beginning in late May. The meadow section near Kirk is prime. Fish are very large — 18–24 inch rainbows on dry flies.
Water Notes
500–1,500 cfs. Water 52–60°F. Outstanding spring conditions. Hex season approaching.
June Outlook
The Williamson River is one of Oregon's finest late-season fisheries for large rainbow trout. The hexagenia hatch in June is one of the most anticipated events in Oregon fly fishing.
Productive Patterns
- Hexagenia Dry
- PMD
- Callibaetis
- Elk Hair Caddis
Tips
The Williamson runs through the Klamath Basin with large, spring-fed flows. The Hexagenia hatch occurs in the evening from late May through June. Fish are very large — 20+ inch rainbows are common.
Water Notes
500–1,500 cfs. Water 54–62°F. Spring-fed flows keep the river consistent.
July Outlook
Callibaetis and PMD hatches produce consistent action on the Williamson. The river's large rainbows are aggressive in July.
Productive Patterns
- Callibaetis
- PMD Sparkle Dun
- Elk Hair Caddis
- Hopper
Tips
The upper Williamson above Klamath Lake is the most productive section. Fish the open meadow stretches for rising fish. The fish are large and require strong tippet.
Water Notes
600–1,200 cfs. Water 56–64°F. Excellent summer conditions on a beautiful southern Oregon river.
August Outlook
August hopper and Callibaetis fishing on the Williamson. The meadow section near Kirk produces excellent surface action. Large rainbows feed aggressively on terrestrials along the grass banks.
Productive Patterns
- Hopper
- Callibaetis Sparkle Dun
- Elk Hair Caddis
- Parachute Adams
Tips
The Williamson's meadow sections near Kirk and above are prime hopper habitat. Fish the grass bank edges carefully. The evening Callibaetis spinner fall is an outstanding August event. Large fish are active until sunset.
Water Notes
500–1,000 cfs. Water 58–65°F. Good summer conditions. Fish the meadow section for hoppers and evening Callibaetis.
September Outlook
Excellent fall fishing on the Williamson. Baetis hatches and the beginning of fall streamer season.
Productive Patterns
- Blue Winged Olive
- Callibaetis
- Streamer
- Elk Hair Caddis
Tips
September on the Williamson is excellent with reduced pressure. The large rainbow trout are in peak condition before fall. Streamer fishing along the undercut banks produces the largest fish.
Water Notes
500–1,000 cfs. Water 52–60°F. Outstanding fall conditions.
October Outlook
October BWO fishing on the Williamson. Fall steelhead are entering the Klamath main stem below — the Williamson produces resident rainbows on fall hatches. Streamer season for large fish.
Productive Patterns
- Blue Winged Olive
- Mahogany Dun
- Streamer
- Soft Hackle
Tips
October is one of the finest months for the Williamson's streamer fishing. Pre-winter rainbows are aggressive and large. The BWO hatch on overcast afternoons produces surface rises. The Kirk section is most productive.
Water Notes
500–1,000 cfs. Water 50–58°F. Good fall conditions. Low pressure.
November Outlook
November on the Williamson is quiet and productive. Late BWO activity continues on mild days. The spring-fed river maintains consistent temperatures through fall.
Productive Patterns
- Blue Winged Olive
- Zebra Midge
- RS2
- Soft Hackle
Tips
November Williamson fishing is solitary and rewarding. The Klamath marsh country is beautiful under late fall skies. Midge and late BWO activity provides consistent fishing. The river's large trout population keeps results good throughout the year.
Water Notes
500–1,000 cfs. Water 48–54°F. Late fall conditions. Consistent spring-fed flows.
December Outlook
December closes the year on the Williamson. Winter midge fishing in a remote southern Oregon marsh setting. The spring-fed river keeps fish active year-round.
Productive Patterns
- Zebra Midge
- RS2
- Mysis Shrimp Pattern
- Soft Hackle Midge
Tips
December on the Williamson is a winter solitude experience. The Chiloquin area provides access to productive winter sections. Midge nymphing in the deeper pools. A quiet, beautiful southern Oregon winter outing.
Water Notes
500–1,200 cfs. Water 46–50°F. Stable spring-fed winter conditions. Remote Klamath Basin setting.
Hatch Calendar
| Insect | Peak | Active | Size | Productive Patterns |
|---|---|---|---|---|
| Hexagenia Hexagenia limbata |
Jun | Jun, Jul | #4–8 |
|
| Pale Morning Dun Ephemerella infrequens |
Jun, Jul | Jun, Jul, Aug | #16–18 |
|
| Blue Winged Olive Baetis spp. |
May, Oct | Apr, May, Sep, Oct, Nov | #18–20 |
|
Access & Approach
Klamath Falls and Chiloquin are the main bases. Float trips dominate; Klamath Tribal lands border parts of the river. Oregon fishing license required; check current Klamath Tribes regulations for tribal sections.
Regulations & License
Fishing in Oregon requires a current license. Always verify season dates, bag limits, and any special-regulation waters before you fish.
Oregon fishing regulations & license →
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About Current
Williamson River conditions on Current combine real-time flow data (USGS, WSC, CDEC, CEHQ), weather, tide predictions, hatch probabilities calibrated to this specific water, and recent fly shop reports from the area.
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