Verified for 2026

Pennsylvania Hatch Chart for Fly Fishing (2026)

Last verified: April 2026. Sources: Pennsylvania Fish & Boat Commission, FlyFishFinder regional charts, Sky Blue Outfitters guide reports, Mountain Laurel Guide Service (Penn's Creek), plus Cast & Tie observations on PA limestone water in 2026.

Pennsylvania has more cold-water trout stream miles than any state east of the Mississippi. The hatch calendar splits cleanly into two columns: limestone spring creeks (Penn's, Spring, Letort, Little Lehigh, Yellow Breeches, Falling Spring) running on stable groundwater temperatures, and freestone streams (Pine, Kettle, Loyalsock, Brodhead, Lehigh) running on air-temperature-driven snowmelt and surface flow. Limestone hatches arrive 1-2 weeks earlier than freestone hatches in spring, and limestone water holds Tricos and BWOs that freestone water doesn't.

This chart covers both streams of water with separate columns where they diverge.

Season snapshot: Pennsylvania (April 2026)

Water What's hatching Best fly Notes
Limestone (Penn's, Spring, Yellow Breeches) Hendrickson, BWO, Grannom caddis Hendrickson parachute, Walt's Worm sub-surface Hendrickson peak: 1-3 pm
Freestone (Brodhead, Pine, Kettle) Quill Gordon, Blue Quill, Hendrickson (later) Quill Gordon parachute, blue quill #16 Freestones running 7-10 days behind limestones

How to read a hatch chart

Pennsylvania hatch dates shift by watershed type, elevation, and air temperature. Penn's Creek limestone water in central PA can hatch Sulphurs three weeks before Pine Creek freestone water in the same calendar week. Use this chart for sequencing and trip planning — confirm specifics with the local fly shop before you drive.

Sizes use standard hook-size notation (smaller hook = larger number). Eastern PA hatches concentrate in the 12-22 range; the Green Drake on Penn's Creek is the rare outlier at #8-10.

Limestone vs. freestone — the calendar split

Hatch Limestone (Penn's, Spring) Freestone (Pine, Kettle, Brodhead)
Hendrickson Mid-April Late April
Sulphur peak Mid-May Late May / early June
Green Drake Late May (Penn's specifically) Sporadic; mostly late-May Brodhead
Trico July-August Largely absent
Fall BWO Sept-Oct Sept-Oct

Month-by-month hatch chart

January

Insect Size Hours Stage Best fly Notable waters
Midges 22-26 Midday All Zebra midge, Griffith's gnat Limestone, statewide
Little black stoneflies 16-18 Late morning Adult Black stonefly Limestone, statewide

February

Insect Size Hours Stage Best fly Notable waters
Midges 22-26 Midday All Zebra midge, RS2 Statewide
Little black stoneflies 16-18 Midday Adult Black stonefly, foam stone Statewide
Early black stoneflies 14-16 Afternoon Adult Stimulator (small) Limestone, freestone

March

Insect Size Hours Stage Best fly Notable waters
Quill Gordon 12-14 Afternoon Dun Quill Gordon parachute Freestone (Brodhead, Pocono)
Blue quill 16-18 Late morning Dun Blue quill parachute Freestone primarily
BWO 18-22 Overcast midday Dun + emerger BWO parachute, RS2 Both
Stoneflies (continued) 14-16 Midday Adult Black stonefly Statewide

April

Insect Size Hours Stage Best fly Notable waters
Hendrickson 12-14 1-3 pm Dun + spinner Hendrickson parachute, red quill spinner Both (limestone earlier)
Grannom caddis 14-16 Late morning Adult + pupa Grannom caddis, Green Weenie sub-surface Limestone (Penn's, Yellow Breeches, Spring Creek)
BWO 18-22 Overcast Dun + emerger BWO parachute Both
Little black caddis 16-18 Afternoon Adult Black caddis Statewide

May

Insect Size Hours Stage Best fly Notable waters
Sulphurs (peak in limestone) 14-18 Evening (7 pm-dark) Dun + spinner Sulphur parachute, sulphur emerger Penn's, Spring, Yellow Breeches, Little Lehigh
March Browns 10-12 Afternoon Dun + spinner March Brown parachute Both
Grey Fox 12-14 Afternoon Dun Grey Fox parachute Both
Green Drake (Penn's Creek) 8-10 Evening into dark Dun + spinner (Coffin Fly) Green Drake comparadun, Coffin Fly Penn's Creek primarily
Light Cahill 12-14 Evening Dun Light Cahill parachute Freestone primarily
Caddis (multiple) 14-18 Afternoon-evening Adult + pupa Elk hair caddis (tan, olive) Both

June

Insect Size Hours Stage Best fly Notable waters
Sulphurs (continued) 14-18 Evening Dun + spinner Sulphur parachute, rusty spinner Limestone primarily
Slate Drake / Isonychia 10-12 Late afternoon-evening Dun + nymph Iso nymph, slate drake parachute Both
Sulphur spinner falls 16-18 Last 30 min of light Spinner Rusty spinner Limestone
Light Cahill 12-14 Evening Dun + spinner Light Cahill, ginger quill spinner Freestone
Inchworms (terrestrial) 14 All day — Green Weenie Statewide
Green Drake spinner fall 10 Last 20 min light Spinner (Coffin Fly) Coffin Fly Penn's Creek tail-end

July

Insect Size Hours Stage Best fly Notable waters
Tricos 22-24 7-10 am Spinner fall Trico spinner, parachute Limestone (Penn's, Spring, Falling Spring)
Slate drake / Iso 10-12 Evening Dun + nymph Iso nymph Both
Terrestrials (peak) 12-16 All day — Ant, beetle, hopper, Green Weenie Statewide
Cinnamon caddis 14-16 Evening Adult Tan elk hair caddis Both

August

Insect Size Hours Stage Best fly Notable waters
Tricos (peak) 22-24 7-10 am Spinner fall Trico spinner Limestone
Terrestrials 12-16 All day — Hopper, ant, beetle Statewide
Caddis (sporadic) 14-16 Evening Adult Tan elk hair caddis Both
Slate drake 10-12 Evening Dun + nymph Iso nymph, slate drake parachute Both

September

Insect Size Hours Stage Best fly Notable waters
BWO (return hatch) 18-22 Overcast midday Dun + emerger BWO parachute, RS2 Both
Slate drake 10-12 Afternoon Dun + nymph Iso nymph Freestone
Trico tail-end 22-24 Morning Spinner fall Trico spinner Limestone
Terrestrials 12-16 All day — Ant, beetle, hopper Statewide

October

Insect Size Hours Stage Best fly Notable waters
BWO 18-22 Midday Dun + emerger BWO parachute Both
October caddis 8-10 Afternoon Adult + pupa October caddis Freestone (Pine, Loyalsock)
Streamer fishing peaks — All day — Sculpin, woolly bugger, Mop Fly Statewide

November

Insect Size Hours Stage Best fly Notable waters
BWO (tail) 20-22 Midday warm overcast Dun BWO parachute, midges Limestone primarily
Midges 22-26 Midday All Zebra midge Statewide
Streamer season — All day — Streamers Statewide

December

Insect Size Hours Stage Best fly Notable waters
Midges 22-26 Midday warm All Zebra midge, RS2 Limestone
Sub-surface — — — Walt's Worm, small nymphs Statewide

Top 5 most important hatches in Pennsylvania

1. Penn's Creek Green Drake (Limestone)

When: Last 10 days of May into first week of June. Peak: Memorial Day weekend ±3 days. Where: Penn's Creek, Centre and Union counties — primarily middle Penn's from Coburn through Weikert. Identification: Massive mayfly. Pale yellow body, pale gray-green wings, size 8-10. Three tails. Coffin Fly (spinner) is white with black markings. Why it matters: The most famous hatch in Eastern fly fishing. Brings out giant browns that haven't fed on the surface since the previous year's hatch. A single week can produce more 18+ inch fish than entire seasons of nymphing. Best patterns:

  • Green Drake comparadun (size 10) — primary dun
  • Coffin Fly parachute — spinner fall
  • Green Drake nymph (large brown nymph) — pre-hatch days

Fishing the hatch: Plan to fish 6 pm to dark. The hatch progresses upstream — if you hit it on the upper section the first night, the lower section will be hatching 24-48 hours later. Crowds are real; the upper sections see fewer anglers and often more fish.

2. Sulphurs (Limestone-wide)

When: Mid-May through end of June. Where: Penn's Creek, Spring Creek, Yellow Breeches, Little Lehigh, Tulpehocken — every PA limestoner. Identification: Pale yellow body, yellowish-tan wings, size 14-18. Three tails. Why it matters: Six weeks of consistent evening dry fly. Wild browns key on Sulphurs more reliably than on any other hatch on limestone water. Best patterns:

  • Sulphur parachute (size 16-18) — primary dun
  • Rusty spinner (size 16-18) — last 30 minutes of light
  • Sulphur emerger / soft-hackle pheasant tail (size 16) — 30 min before duns surface

Fishing the hatch: Position above productive runs by 6 pm. Watch the air for spinners before duns appear. Spinner fall is when fish move to the heads of pools and feed in regular intervals.

3. Hendrickson (statewide)

When: Mid-April to early May. Where: All PA trout water; limestone earlier than freestone. Identification: Reddish-brown body, slate gray wings, size 12-14. Why it matters: First major mayfly hatch of the year. Fish that have eaten midges and stones for four months turn aggressive. Best patterns:

  • Hendrickson parachute (size 14)
  • Red quill spinner (size 12-14)
  • Pheasant tail (size 14) — sub-surface emerger

Fishing the hatch: 1-3 pm. Slow tailouts and pool heads. Spinner falls happen the following morning — be on water at 9-10 am if conditions allow.

4. Trico Spinner Fall (Limestone)

When: Mid-July through mid-September. Where: Penn's Creek, Spring Creek, Letort, Falling Spring, Yellow Breeches, Little Lehigh. Identification: Tiny — size 22-24. Black body on the female, lighter on the male. Distinctive "blizzard" of spinners over the surface. Why it matters: Six-plus weeks of morning fishing in the dog days when nothing else is happening. Trout sip spinners in classic dry-fly form — exactly the fishing limestone anglers chase. Best patterns:

  • Trico spinner (size 22-24)
  • Trico parachute (size 22) — for fish refusing the spent spinner
  • Cluster (size 18-20) — rough water and bigger fish

Fishing the hatch: 7-10 am. 6X-7X tippet minimum. Long leaders (12-14 ft) with longer drag-free drifts than any other PA hatch.

5. Sulphurs (Penn's Creek specifically)

When: Late May through mid-June. Where: Penn's Creek lower section. Identification: Same as the limestone-wide Sulphur but Penn's gets denser hatches than any other PA water. Why it matters: Penn's combines Sulphur density with the year's largest wild browns moving onto the dun. The two-week overlap with the Green Drake creates the most productive 14 days on the East Coast for surface trophy fishing.

Cold-water vs. freestone hatch differences

PA limestone streams (Penn's, Spring, Letort, Little Lehigh, Falling Spring, Yellow Breeches, Tulpehocken) run on stable 50-60°F groundwater year-round. Hatches arrive 1-2 weeks earlier in spring than on freestones at similar latitude. Limestone water holds Tricos that freestones don't. The midge hatch on limestone is heavier and runs through the full winter.

PA freestones (Pine Creek, Kettle Creek, Loyalsock, Brodhead, Lehigh, Pocono trout streams) follow snowmelt and air temperatures. Quill Gordons and Blue Quills appear early on freestones in March-April; limestone water rarely shows them. October Caddis is a freestone hatch — limestone misses it.

The practical implication: in early April, drive to a limestoner. In October, drive to a freestone. The hatch calendar tells you where to fish, not just what to tie on.

Sources and verification

Where to fish each hatch

Patterns for Pennsylvania hatches

  • Walt's Worm — Walt Young's PA-origin nymph; covers Hendrickson + caddis sub-surface across the season
  • Green Weenie — terrestrial peak, Pennsylvania-origin pattern
  • Mop Fly — heavy point fly for high-water windows in spring runoff

Last verified: April 2026. Updated quarterly. Next scheduled review: July 2026.