When does the Sulphur hatch occur?

The Sulphur (Ephemerella dorothea / invaria) hatch runs from April through September across Eastern US rivers, with peak activity typically in May or June. Earlier on lower-elevation southern rivers, later on northern and high-elevation streams.

What flies match the Sulphur hatch?

Standard Sulphur fly patterns include Sulphur Parachute #16-18, Sulphur Comparadun #16-18, Sulphur Sparkle Dun #16, Pheasant Tail Nymph #16, Sulphur Spinner #18. The most important mayfly hatch on Eastern rivers. Reliable emergence + spinner fall every evening for 4-6 weeks. Match the spinners with rusty-bodied patterns.

What water temperature triggers the Sulphur hatch?

Sulphur emergence triggers at water temperatures of 55–68°F, with peak activity around 62°F. Read your thermometer, not your calendar.

What time of day does the Sulphur hatch?

The Sulphur hatch typically emerges in the evening. Plan your fishing window around that — being on the water before the emergence starts is more important than being on the water early in general.

Sulphur (Ephemerella dorothea / invaria) Hatch — Timing & Fly Patterns

Hatch profile

Sulphur

Ephemerella dorothea / invaria

MayflyEvening6-week run

Water temperature trigger

Range: 55–68°F · Peak: 62°F

Fly patterns

Sulphur Parachute #16-18
Sulphur Comparadun #16-18
Sulphur Sparkle Dun #16
Pheasant Tail Nymph #16
Sulphur Spinner #18

Also known as

Pale Watery · Little Yellow May

The most important mayfly hatch on Eastern rivers. Reliable emergence + spinner fall every evening for 4-6 weeks. Match the spinners with rusty-bodied patterns.

Best rivers for the Sulphur hatch

These rivers list the Sulphuras a signature hatch — the local fly shops and angling history confirm it's reliable enough to plan a trip around.

Pennsylvania
Penns Creek
Peak: May 20 – Jun 25
Intensity: heavy
Pennsylvania
Spring Creek
Peak: May 20 – Jun 25
Intensity: heavy
Pennsylvania
Brodhead Creek
Peak: May 25 – Jun 25
Intensity: heavy
Pennsylvania
Letort Spring Run
Peak: May 20 – Jun 25
Intensity: heavy
Pennsylvania
Yellow Breeches Creek
Peak: May 20 – Jun 25
Intensity: heavy
Pennsylvania
Big Fishing Creek
Peak: May 25 – Jun 25
Intensity: heavy
Pennsylvania
Loyalsock Creek
Peak: May 25 – Jun 25
Intensity: heavy
Pennsylvania
Falling Springs Branch
Peak: May 20 – Jun 25
Intensity: heavy
Pennsylvania
Little Juniata River
Peak: May 20 – Jun 25
Intensity: heavy
Pennsylvania
Upper Delaware River
Peak: May 25 – Jul 5
Intensity: heavy
New York
West Branch Delaware River
Peak: May 25 – Jul 5
Intensity: heavy
New York
Beaverkill River
Peak: Jun 1 – Jun 30
Intensity: heavy
New York
Esopus Creek
Peak: Jun 1 – Jun 30
Intensity: heavy
Virginia
New River
Peak: May 5 – Jun 1
Intensity: heavy
Virginia
Mossy Creek
Peak: May 20 – Jun 25
Intensity: heavy
Virginia
Rose River
Peak: May 20 – Jun 25
Intensity: heavy
Virginia
Roaring Run
Peak: May 20 – Jun 25
Intensity: heavy
Virginia
Jackson River
Peak: May 25 – Jul 5
Intensity: heavy
West Virginia
Cranberry River
Peak: May 20 – Jun 25
Intensity: heavy
West Virginia
Elk River (headwaters)
Peak: May 20 – Jun 25
Intensity: heavy
West Virginia
Shavers Fork
Peak: May 20 – Jun 25
Intensity: heavy
West Virginia
North Fork South Branch Potomac
Peak: May 25 – Jun 25
Intensity: heavy
North Carolina
Davidson River
Peak: May 20 – Jun 25
Intensity: heavy
North Carolina
South Toe River
Peak: May 20 – Jun 25
Intensity: heavy
North Carolina
Nantahala River
Peak: May 25 – Jul 5
Intensity: heavy
North Carolina
Chattooga River (upper)
Peak: May 20 – Jun 25
Intensity: heavy
North Carolina
Watauga River (NC)
Peak: May 25 – Jul 5
Intensity: heavy
Tennessee
South Holston River
Peak: May 15 – Aug 15
Intensity: heavy
Tennessee
Watauga River (TN)
Peak: May 25 – Jul 5
Intensity: heavy
Tennessee
Clinch River
Peak: May 1 – Jun 15
Intensity: heavy
Tennessee
Caney Fork River
Peak: May 25 – Jul 5
Intensity: heavy
Georgia
Chattahoochee River (upper)
Peak: May 25 – Jul 5
Intensity: heavy
Georgia
Toccoa River
Peak: May 25 – Jul 5
Intensity: heavy
Georgia
Conasauga River
Peak: May 20 – Jun 25
Intensity: heavy
Maryland
Gunpowder Falls
Peak: May 25 – Jul 5
Intensity: heavy
Maryland
Big Gunpowder Falls (freestone upper)
Peak: May 25 – Jun 25
Intensity: heavy
Maryland
North Branch Potomac River
Peak: May 25 – Jul 5
Intensity: heavy
New Jersey
South Branch Raritan River
Peak: May 20 – Jun 25
Intensity: heavy
New Jersey
Musconetcong River
Peak: May 25 – Jun 25
Intensity: heavy
Connecticut
Farmington River
Peak: May 25 – Jul 5
Intensity: heavy
Connecticut
Housatonic River
Peak: Jun 1 – Jul 5
Intensity: heavy
Vermont
Battenkill River
Peak: Jun 1 – Jul 5
Intensity: heavy
Vermont
Lamoille River
Peak: Jun 10 – Jul 10
Intensity: heavy
New Hampshire
Upper Connecticut River
Peak: Jun 10 – Jul 10
Intensity: heavy
Maine
Kennebago River
Peak: Jun 10 – Jul 10
Intensity: heavy
Maine
Rapid River
Peak: Jun 10 – Jul 10
Intensity: heavy

Other rivers with Sulphur activity

These rivers carry the hatch but at varying intensity — check each river's page for the local peak window.

Willowemoc Creek (New York)
Neversink River (New York)
Rondout Creek (New York)
Rapidan River (Virginia)

Get a notification when the Sulphur is on.

Bield: Fish ties USGS gauge readings to hatch triggers and alerts you when your home river hits the temperature window for the hatch you're waiting on.

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