Most Popular Hatches in May For Fly Fishing
May is a transformative month for fly fishing across the United States. As rivers swell with snowmelt and aquatic life bursts forth, trout become increasingly active, feeding on a variety of emerging insects. Understanding the key hatches during this period can significantly enhance your angling success. Here's a comprehensive guide to the top 10 May hatches, complete with effective fly patterns and tactical tips.
Pale Morning Dun (PMD)
Timing: Mid-morning to early afternoon
Size: 14–18
Water Type: Tailwaters, spring creeks, and freestone rivers
PMDs are a staple hatch throughout the U.S., especially in tailwaters and spring creeks. These light-colored mayflies hatch mid-morning to early afternoon and often bring selective trout to the surface.
Tips & Techniques:
Focus on riffles, seams, and transitions from shallow to deeper water where duns are likely to emerge.
Use 5X–6X tippet and a longer leader to improve presentation during slow or clear water conditions.
Adjust between nymphs, emergers, and spinners as the hatch progresses throughout the morning and early afternoon.
Must-Have Patterns:
PMD Sparkle Dun
PMD Parachute
PMD Spinner
Related: Understanding Trout Feeding For Better Fishing Results
Mother's Day Caddis
Timing: Mid-May
Size: 14–16
Water Type: Western and Midwestern rivers
Mother’s Day Caddis hatches are among the most prolific spring events, often blanketing rivers in mid-May. Trout feed aggressively on both emerging pupae and fluttering adults.
Tips & Techniques:
Fish soft hackles or pupae subsurface before the hatch fully develops.
Switch to skating or twitching dries as trout begin to rise.
Target seams, riffles, and back eddies where adults collect in numbers.
Must-Have Patterns:
Elk Hair Caddis – Olive
Beadhead Soft Hackle Pheasant Tail
Deer Hair Sparkle Caddis
Blue-Winged Olive (BWO)
Timing: March through May
Size: 16–20
Water Type: Tailwaters, spring creeks, and freestones on cloudy days
BWOs are a consistent hatch in spring, especially on overcast days. Trout feed on them throughout their life cycle, from nymphs to spinners.
Tips & Techniques:
Fish nymphs during the morning and switch to emergers or dries as the hatch progresses.
Use a dead-drift presentation with light tippet for a natural drift.
Focus on slower water and eddies where trout feed on emerging insects.
Must-Have Patterns:
Parachute Blue Wing Olive
Beadhead RS2
Zebra Midge
March Brown
Timing: Late April through May
Size: 12–14
Water Type: Freestone rivers and streams
March Browns are larger mayflies that hatch sporadically, often bringing big trout to the surface.
Tips & Techniques:
Fish nymphs in the morning and switch to dries during the afternoon hatch.
Use a downstream presentation to avoid spooking fish.
Target riffles and runs where trout are likely to be feeding.
Must-Have Patterns:
March Brown Parachute
Flashback Hare's Ear
March Brown Wet
Related: Learning The Art of Fly Fishing
Skwala Stonefly
Timing: March through May
Size: 10–12
Water Type: Western freestone rivers
Skwalas are one of the first significant stonefly hatches of the year, providing early dry fly action.
Tips & Techniques:
Fish along banks and slower water where adults crawl out to hatch.
Use large, buoyant dries to imitate adult stoneflies.
Add movement to your fly to mimic the natural behavior of stoneflies.
Must-Have Patterns:
Skwala Stimulator
Pat's Rubber Legs
Elk Hair Caddis (for smaller stoneflies)
Midges
Timing: Year-round
Size: 18–24
Water Type: Tailwaters and spring creeks
Midges are a constant food source for trout, especially in colder waters.
Tips & Techniques:
Use light tippet (6X–7X) for a natural presentation.
Fish tandem rigs with a midge pupa and emerger.
Focus on slow-moving water where trout sip midges near the surface.
Must-Have Patterns:
Zebra Midge
Griffith's Gnat
WD-40
Green Drake
Timing: Late May through June
Size: 10–12
Water Type: Freestone rivers and streams
Green Drakes are large mayflies that create explosive feeding behavior in trout.
Tips & Techniques:
Fish during overcast days or evenings when hatches are most prolific.
Use large, visible dries to match the size of the natural insect.
Target slower water where trout have more time to inspect your fly.
Must-Have Patterns:
Green Drake Parachute
Green Drake Emerger
Royal Wulff (as an attractor)
Yellow Sally
Timing: May through July
Size: 14–16
Water Type: Western rivers and streams
Yellow Sallies are small stoneflies that hatch in large numbers, providing consistent dry fly action.
Tips & Techniques:
Fish near banks and in pocket water where adults emerge.
Use high-floating dries with a touch of yellow to match the hatch.
Add slight movement to your fly to mimic the fluttering of the natural insect.
Must-Have Patterns:
Yellow Sally Stimulator
Yellow Elk Hair Caddis
Yellow Sally Parachute
Hendrickson
Timing: April through May
Size: 12–14
Water Type: Eastern rivers and streams
Hendricksons are a key early-season hatch in the East, bringing large trout to the surface.
Tips & Techniques:
Fish nymphs in the morning and switch to dries during the afternoon hatch.
Use a downstream presentation to avoid spooking fish.
Target riffles and runs where trout are likely to be feeding.
Must-Have Patterns:
Hendrickson Parachute
Hendrickson Spinner
Pheasant Tail Nymph
Dark Cahill
Timing: May through June
Size: 14–16
Water Type: Eastern rivers and streams
Dark Cahills are important mayflies in the East, often hatching in the evening.
Tips & Techniques:
Fish during low-light conditions when hatches are most active.
Use dark-bodied dries to match the natural insect.
Target slower water where trout feed more deliberately.
Must-Have Patterns:
Dark Cahill Dry
Dark Cahill Spinner
Adams
Dark Cahill
Timing: May through June
Size: 14–16
Water Type: Eastern rivers and streams
Dark Cahills don’t get the Instagram fame of Green Drakes or BWOs, but don’t let that fool you. When twilight hits and the bugs start lifting, trout will be cruising for these late-evening mayflies like it’s happy hour.
Tips & Techniques:
Hit the water during the golden hour—just before dusk.
Use dark-bodied patterns to stand out against the reflective water.
Focus on slow runs and tailouts, where trout sip cautiously.
Must-Have Patterns:
Dark Cahill Dry
Adams (a classic, effective crossover)
Comparadun Cahill
FAQs
What is the most important hatch in May for fly fishing?
The Pale Morning Dun (PMD) and Mother’s Day Caddis are two of the most prolific and predictable hatches during May across many regions in the U.S.
How do I know which hatch is happening?
Look for rising fish, insect activity above the water, and check the undersides of streamside rocks. You can also match what's flying around to your fly box.
What’s the best fly size for May hatches?
It varies by hatch, but most fall between size 12 and 18. BWOs can go smaller (18–22), while Green Drakes and Skwalas require larger flies (10–12).
Should I fish dry flies or nymphs during a hatch?
Start with nymphs and emergers. As the hatch intensifies and trout begin rising, switch to dry flies or spinners. Match what trout are actually feeding on.
What’s a good all-around fly pattern for May?
The Parachute Adams is a solid fallback for various mayflies. The Elk Hair Caddis is another versatile dry fly for May caddis hatches.
Where is the best place to fish during a hatch?
Look for seams, riffles, and foam lines—places where current concentrates insects. During spinner falls, focus on slower water and tailouts.
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