Fly Fishing Hatch Calendar by Region

Timing a hatch correctly is more valuable than any rod upgrade. The right fly on empty water catches nothing. The right fly during an active hatch — when fish are positioned, feeding, and committed — is how memorable days happen.

This calendar breaks down key hatch windows by region, with water temperature thresholds and the fly patterns that match each emergence. Use OnX Maps to identify access points and plan entry routes before each window opens. Use Orvis for fly boxes built around regional patterns.

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North America: Pacific Northwest

Key Hatches

Baetis (Blue-Winged Olive Mayfly): April–June, water temps 50–55°F. Parachute Adams and pheasant tail nymphs in sizes 16–20.
Cinygnetra (Pale Morning Dun): May–July, water temps 52–58°F. Focus on midges and emerger patterns in the morning.
Golden Stoneflies: October–November, water temps 55–60°F. Target riffles and runs with large dry flies and streamers.

Use OnX to map river access along watershed corridors before each hatch window. Pacific Northwest rivers often cross mixed public and private land — knowing your legal entry points before you drive saves trips.

North America: Eastern United States

Key Hatches

Blue-Winged Olive (BWO): Spring and fall, water temps 50–55°F. Parachute Adams and pheasant tails in sizes 18–22. BWOs hatch on overcast, drizzly days — don't write off a gray afternoon.
Caddisflies: Summer, water temps 60–65°F. Elk hair caddis and wet fly emergers in sizes 14–18. Evening hatches are most productive.
Sulphur (Mayfly): April–May, water temps 52–56°F. Sulphur dry flies and nymphs in sizes 14–16. One of the most reliable Eastern hatch windows of the season.

Eastern rivers like the Delaware, Brodhead, and Gunpowder have significant private stretches. Use OnX to confirm public access and identify wade entry points before any new water.

Europe: Alpine Regions

Key Hatches

Baetis (Mayfly): May–June, water temps 12–15°C. Dry flies and nymphs in sizes 16–20.
Ephemerella (Mayfly): June–July, water temps 14–16°C. Emergers and dry flies in sizes 14–18.
Green Drake (Mayfly): July–August, water temps 16–18°C. Large dry flies and streamers in sizes 8–12. The most visible and exciting Alpine hatch of the season.

Alpine stream access varies significantly by canton and country. Research local regulations and access permissions well before arrival.

Australia: Southeast Coast

Key Hatches

Greenhead (Mayfly): November–December, water temps 18–22°C. Dry flies and nymphs in sizes 12–16.
Caddisflies: Spring, water temps 16–19°C. Wet flies and emergers. Hatches concentrate in shaded pools during afternoon hours.
Midge Hatches: Year-round, water temps 14–25°C. Midge patterns and small streamers. Reliable when larger species are inactive.

How to Use This Calendar

Water temperature is a more reliable trigger than calendar date. Cross-reference these windows against live USGS gauge data (or regional equivalents) before committing to a trip. A hatch that "should" be happening in late June can run two weeks early after a warm spring — or two weeks late after a cold one.

Build your access scouting ahead of time. When conditions break on a Tuesday, having already mapped your entry points via OnX Maps means you can move on it instead of defaulting to familiar, pressured water.

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