Northern Colorado
Hatch Calendar
Monthly hatch activity for the Poudre River, Big Thompson, North Platte, and Horsetooth.
| Hatch | January | February | March | April | May | June | July | August | September | October | November | December |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Blue Winged Olive #18–24 | Active | Peak | Active | Active | Peak | Active | ||||||
Midge #20–28 | Peak | Peak | Peak | Active | Active | Active | Active | Active | Active | Active | Peak | Peak |
Pale Morning Dun #16–20 | Active | Peak | Peak | Active | ||||||||
Green Drake #10–14 | Peak | Peak | ||||||||||
Trico #20–26 | Peak | Peak | Active | |||||||||
Caddis #14–18 | Active | Peak | Peak | Active | Peak | Peak | Active | |||||
Golden Stonefly #6–10 | Peak | Peak | Active | |||||||||
Salmonfly #4–8 | Peak | Peak | ||||||||||
Hoppers, Ants & Beetles #8–14 | Peak | Peak | Active |
Hatch Details
Blue Winged Olive
Baetis (BWO)
Sizes
#18–24
Active Months
March, April, May, September, October, November
Dry Pattern
Parachute BWO, Sparkle Dun, CDC BWO
Nymph Pattern
Pheasant Tail, RS2
Best on overcast, drizzly days. Hatches often occur mid-afternoon. Look for rising fish in slower pools and eddies.
Midge
Chironomid
Sizes
#20–28
Active Months
January, February, March, April, May, June, July, August, September, October, November, December
Dry Pattern
Griffith's Gnat, Midge Cluster
Nymph Pattern
Zebra Midge, Mercury Midge, Disco Midge
Year-round staple. Critical in winter when few other insects are active. Look for midging fish near the surface in slow water.
Pale Morning Dun
Ephemerella
Sizes
#16–20
Active Months
May, June, July, August
Dry Pattern
Parachute PMD, PMD Cripple, Sparkle Dun PMD
Nymph Pattern
PMD Nymph, Pheasant Tail, Hare's Ear
Reliable summer hatch on all Northern Colorado rivers. Often hatches late morning into early afternoon. Cripple patterns frequently outfish standard dries.
Green Drake
Drunella grandis
Sizes
#10–14
Active Months
June, July
Dry Pattern
Parachute Green Drake, Wulff Green Drake
Nymph Pattern
Green Drake Nymph, Hare's Ear
The most anticipated hatch of the year. Large mayflies that bring up big fish. Typically hatches late afternoon on the Poudre River. Can be explosive when it lines up.
Trico
Tricorythodes
Sizes
#20–26
Active Months
July, August, September
Dry Pattern
Trico Spinner, CDC Trico, Parachute Trico
Nymph Pattern
Trico Nymph, Pheasant Tail
Early morning (7–10am) spinner fall creates incredible midge-like rises. Tiny flies require fine tippet (6x–7x). Best on the North Platte and lower Poudre River.
Caddis
Brachycentrus / Rhyacophila
Sizes
#14–18
Active Months
April, May, June, July, August, September, October
Dry Pattern
Elk Hair Caddis, X-Caddis, Goddard Caddis
Nymph Pattern
Beadhead Caddis, Czech Nymph, Soft Hackle
Caddis are everywhere from late April through October. Evening hatches can be phenomenal. Skating a dry across the surface often triggers explosive strikes.
Golden Stonefly
Hesperoperla / Claassenia
Sizes
#6–10
Active Months
May, June, July
Dry Pattern
Stimulator, Yellow Sally, Madame X
Nymph Pattern
Kaufmann's Stone, Beadhead Golden Stone
Early summer stonefly hatch. Egg-laying females crash on the surface and create aggressive strikes. Fish along banks and riffles in the evening.
Salmonfly
Pteronarcys californica
Sizes
#4–8
Active Months
May, June
Dry Pattern
Kaufmann's Stimulator, Sofa Pillow, Chernobyl Ant
Nymph Pattern
Giant Black Stonefly Nymph
Not present on all Northern Colorado waters but can occur on the upper Poudre River. Massive insects that bring up the biggest browns. Short 2-week window.
Hoppers, Ants & Beetles
Terrestrials
Sizes
#8–14
Active Months
July, August, September
Dry Pattern
Dave's Hopper, Fat Albert, Chernobyl Ant, Black Foam Beetle
Mid-summer through early fall. Cast hoppers tight to grassy banks. Ants and beetles are great searching patterns throughout the day.