Au Sable River
Grayling to Mio · Holy Water
N Michigan, USA
Open live forecast →Target species: Brown and Brook.
Stream gauge: 04136000. Flow and water temperature update on every refresh.
Weekly AI Outlook as of 06/05/26
At 944 cfs and 64.2°F, the Au Sable is running higher than typical June levels but still fishable with excellent water temps for the approaching Brown Drake emergence. With warm evenings forecast (lows in the 50s), we're in the prime window for mid-June's most celebrated hatch. Focus on evening sessions after 8pm when drakes begin moving — nymph patterns during the day, then switch to dries as spinners return. The higher flow will concentrate fish in softer water.
- Flow: 944 cfs — above typical 400-700 range but manageable. Fish will be in softer edges and tailouts, not fighting current
- Hatches: Brown Drake emergence window opening with 64°F water. Evening hatches after 8pm through midnight expected
- Water Temp: 64.2°F — ideal for drake activity. Spring-fed consistency means reliable temps despite air swings
- Best Window: Prime time 8pm-midnight. Nymph deep runs during day, switch to drakes as spinners return after dark
Generated weekly from live USGS gauge readings, weather forecasts, and recent fly shop reports. Updates Friday mornings.
About this Water
- Spring Creek
- Best months: June–Sept, peak June–July (Hex) & Aug (Trico)
The Au Sable River is the birthplace of American fly fishing tradition and the founding river of Trout Unlimited. Cold, spring-fed and gin-clear, it flows through northern Michigan's jack pine barrens producing outstanding trout fishing for large brown trout in the storied Holy Water section between Grayling and Mio. The Au Sable's night fishing tradition — floating logs in darkness with big flies — is an American original.
The Au Sable's Hexagenia mayfly hatch — the world's largest mayfly species — brings 20-inch brown trout to the surface at midnight in late June.
January Outlook
January on the Au Sable is deep Michigan winter. The spring-fed river stays open and above freezing — a remarkable feature that makes it fishable year-round. Midge nymphs and Baetis produce fish in the Holy Waters section.
Productive Patterns
- Zebra Midge
- RS2
- Baetis Nymph
- Soft Hackle Midge
Tips
The Au Sable's spring-fed character keeps the water 48–52°F year-round, even when air temps are well below zero. Fish the Holy Waters section near Grayling. Access is limited to the fly-fishing-only section from Burton's Landing. Winter gear essential.
Water Notes
Spring-fed 400–650 cfs. Water 46–52°F year-round. Rarely freezes due to spring inputs. Cold Michigan winter — dress appropriately.
February Outlook
February on the Au Sable is quiet and productive. The spring-fed river remains above freezing while northern Michigan is in deep winter. Midge fishing in the Holy Waters section.
Productive Patterns
- Zebra Midge
- RS2
- Midge Pupa
- Soft Hackle
Tips
February is the most peaceful month on the famous Au Sable. The spring-fed water keeps conditions consistent. Fish the slow pools near the public access points in the Holy Waters section. Snowshoes may be needed to access certain sections.
Water Notes
Spring-fed 400–650 cfs. Water 46–52°F. Ice along margins in cold snaps but main channel stays open. Deep Michigan winter above ground.
March Outlook
March on the Au Sable. The first Baetis activity begins on mild afternoons as spring approaches. The spring-fed river has been consistent all winter — now the hatches start building.
Productive Patterns
- Baetis Sparkle Dun
- Midge Dry
- RS2
- Elk Hair Caddis (small)
Tips
March on the Au Sable is a preview of the season. Early Baetis activity on sunny afternoons. The Holy Waters section begins seeing increasing angler traffic as the season approaches. A quiet, productive early-spring visit.
Water Notes
Spring-fed 400–700 cfs. Water 48–54°F. Early spring transitioning. First Baetis activity of the year.
April Outlook
April on the Au Sable is the awakening. Early Hendrickson nymphs become active. The Quill Gordon may appear by month's end. The Holy Waters section is coming to life after winter.
Productive Patterns
- Quill Gordon
- Baetis Sparkle Dun
- Blue Quill
- Soft Hackle Emerger
Tips
The Quill Gordon and early Hendrickson activity in late April on the Au Sable can be spectacular. These are the first major hatches of the year. Fish the evening window from 4–7pm when the first adults appear.
Water Notes
Spring-fed 400–700 cfs. Water 48–54°F. Spring approaching. Early hatches building toward May peak.
May Outlook
The Au Sable River in Michigan is one of the finest spring creek-style freestone rivers in the Midwest. Hendrickson hatch begins in May.
Productive Patterns
- Hendrickson Dry
- Sulphur
- Blue Winged Olive
- Soft Hackle Emerger
Tips
The Holy Waters section from Grayling to Mio is fly-fishing-only. The Hendrickson hatch in May is the first major event of the year. Fish the evening hatch carefully.
Water Notes
Spring-fed flows 400–700 cfs. Water 48–54°F year-round due to spring inputs. The Au Sable never gets too warm or too cold.
June Outlook
The famous Brown Drake hatch on the Au Sable occurs in mid-June. One of the Midwest's most anticipated annual events.
Productive Patterns
- Brown Drake Dry #10
- Brown Drake Spinner
- Sulphur
- Hex Nymph
Tips
The Brown Drake hatch produces some of the year's largest rising fish. It typically occurs for 7–14 days in mid-June. The evening hatch begins after 8pm and can last until midnight.
Water Notes
400–700 cfs. Water 52–58°F. The spring-fed Au Sable stays cool throughout summer.
July Outlook
The Hexagenia limbata hatch — the most famous hatch on the Au Sable — occurs from late June through July. Fish rise to the largest mayfly in North America.
Productive Patterns
- Hex Dry #6
- Hex Spinner
- Brown Drake
- Sulphur
Tips
The Hex hatch begins after dark — typically 10pm to midnight. Float the Holy Waters in a canoe for the best access. Bring a headlamp and warm clothing. This is one of North American fly fishing's great events.
Water Notes
400–700 cfs. Water 52–58°F. Night fishing is the norm during the Hex hatch. The Au Sable's spring-fed character keeps summer temps ideal.
August Outlook
Post-Hex season on the Au Sable with consistent Trico and Caddis activity. Terrestrials are productive in August.
Productive Patterns
- Trico Spinner
- Elk Hair Caddis
- Hopper
- Parachute Ant
Tips
The Au Sable post-Hex season is excellent with Trico spinner falls at dawn and reliable caddis evening hatches. Terrestrials produce well along the forested banks.
Water Notes
350–650 cfs. Water 54–60°F. Consistent spring-fed conditions.
September Outlook
Excellent fall fishing with Caddis and Baetis activity. Brown trout begin pre-spawn behavior. A beautiful Midwest autumn fishery.
Productive Patterns
- Blue Winged Olive
- Elk Hair Caddis
- Streamer
- Soft Hackle
Tips
The Au Sable in September is excellent — the Hartwick Pines section is beautiful in fall foliage. Brown trout streamer fishing in the deeper pools produces large fish.
Water Notes
300–600 cfs. Water 50–58°F. Good fall conditions on the spring-fed river.
October Outlook
Brown trout spawning season. Steelhead runs begin on the main river. Excellent streamer fishing through October.
Productive Patterns
- Streamer
- Egg Pattern
- Woolly Bugger
- Stonefly Nymph
Tips
October is the Au Sable's big fish month. Brown trout spawning activity and early steelhead runs from Lake Huron make this one of the most exciting months.
Water Notes
400–800 cfs. Water 48–56°F. Good fall conditions for both resident browns and spawning fish.
November Outlook
November steelhead season on the lower Au Sable below Lake Huron. Resident brown trout post-spawn in the upper spring-fed sections. The river transitions to winter.
Productive Patterns
- Egg Pattern
- Streamer
- Woolly Bugger
- Soft Hackle
Tips
November brings steelhead from Lake Huron into the lower Au Sable. The upper Holy Waters section produces post-spawn brown trout. The spring-fed water stays consistent even as northern Michigan enters deep fall.
Water Notes
400–800 cfs. Water 46–52°F. Steelhead in lower river. Post-spawn browns in upper spring-fed sections.
December Outlook
December on the Au Sable is winter fishing. The spring-fed river stays open while northern Michigan freezes. Midge and Baetis nymph fishing in the Holy Waters section.
Productive Patterns
- Zebra Midge
- RS2
- Soft Hackle
- Baetis Nymph
Tips
December on the Au Sable is a testament to the spring-fed river's resilience. The river stays open and fishable when everything else is frozen. Midge nymphing in the Holy Waters section. Late steelhead in the lower river.
Water Notes
Spring-fed 400–650 cfs. Water 46–52°F. Ice margins but main channel open. A uniquely productive Michigan December.
Hatch Calendar
| Insect | Peak | Active | Size | Productive Patterns |
|---|---|---|---|---|
| Hex (Giant Mayfly) Hexagenia limbata |
Jun | Jun, Jul | #4–6 |
|
| Hendrickson Ephemerella subvaria |
Apr, May | Apr, May | #12–14 |
|
Access & Approach
Grayling, MI is the gateway city. Multiple public access sites along the mainstream. Gates Au Sable Lodge is the historic anchor shop. Michigan trout license + DNR trout stamp required.
Nearby Fly Shops
- Old Au Sable Fly Shop
- Gates Au Sable Lodge
- Mangled Fly
- The Northern Angler
- Hawkins Outfitters
Regulations & License
Fishing in Michigan requires a current license. Always verify season dates, bag limits, and any special-regulation waters before you fish.
Michigan fishing regulations & license →
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About Current
Au Sable 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.
Au Sable River is one of 245 hand-curated waters in Current. The app and web forecast also generate AI outlooks for any unlisted river, lake, or saltwater flat anywhere in the world — drop a pin or paste a name and Current produces a fresh seasonal outlook with weather, flow context, and recommended techniques.
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