August Fly Fishing Hatch Chart

Quick Answer: What Flies Hatch in August?

In August, trout anglers should be ready for Tricos, grasshoppers, ants, beetles, caddisflies, Pale Morning Duns, Blue-Winged Olives, midges, and stillwater insects such as Callibaetis and damselflies. The exact mix depends on your region and water type, but the basic late-summer pattern is consistent: fish small mayflies early, terrestrials along the banks later, and caddis toward evening.

August is also a month when timing and water temperature matter as much as fly selection. Low, clear water can make trout selective, while hot afternoons can make catch-and-release fishing unsafe. Carry small dries, a few buoyant terrestrials, slim nymphs, and a stream thermometer. Let the water tell you whether to change flies, change locations, or call it a day.

August Fly Fishing Hatch Chart at a Glance

Important: A hatch chart shows a likely progression, not an exact appointment. Elevation, latitude, water temperature, dam releases, rainfall, and local weather can shift an August hatch by days or even weeks. Use this guide to prepare your box, then check a local river report and watch the water before tying on.

Tricos: August's Early-Morning Main Event

Tricos are tiny mayflies that can create one of the most concentrated feeding events of late summer. In the East, they are commonly about size 20-28; Western Tricos are often slightly larger, around size 18-24. They usually begin in July and can continue nearly every morning into fall.

What anglers call the "Trico hatch" is often the spinner fall. Male Tricos emerge overnight, females emerge in the morning, and the adults mate before falling spent onto the water. On warm August days, this sequence can happen shortly after sunrise. Cooler weather usually pushes it later.

Where and How to Fish a Trico Hatch

Look for quiet, rhythmic sipping in slow pools, glides, tailouts, and the softer water below riffles. A black size 18 or 20 Foam Case Spinner gives trout the flat, spent-wing profile they expect. Use light tippet, cast carefully, and prioritize a drag-free drift over constant recasting.

If seeing the fly is the hardest part, fish a double-dry rig. Use a visible size 18 Parachute Adams as the lead fly and trail the smaller spinner 12-24 inches behind it. Watch the Adams; if a fish rises near the trailing fly, set the hook.

Redd's tip: Do not stand in the fast riffle and stare only at the bubbles. The best Trico feeding often happens where the current softens and thousands of spent insects collect.

Terrestrials: Hoppers, Ants, Beetles, and Other Bank Food

By August, many aquatic hatches are smaller or shorter, but land insects are fully active. Grasshoppers, ants, beetles, crickets, inchworms, caterpillars, and other terrestrials reach trout by falling, jumping, or blowing into the water. They do not hatch from the river, but they can still become the most important food on it.

Hoppers are especially important on Western rivers bordered by open valleys, ranchland, and grass. In the East and Midwest, ants and beetles are often more consistent, although hopper patterns still work as searching dries. On large, windy water, try a Keller's Hopper. On smaller streams or around selective fish, downsize to a Baby Hopper or the compact size 16 Micro Chubby.

How to Fish Terrestrials in August

Cast close to grassy banks, undercuts, overhanging limbs, shaded edges, and wind-blown shorelines. Let the fly land with a gentle plop - enough to suggest a clumsy insect, but not enough to make every trout in the pool reconsider its life choices. Start with a clean drift, then try one small twitch if the fly passes through the best water untouched.

When you need a larger, buoyant searching pattern with a different silhouette, Amy's Ant can cover hoppers, beetles, stoneflies, and other chunky terrestrials while carrying a dropper. It is an attractor rather than a precise imitation, which is often useful when no single bug is dominating.

Caddisflies: The Reliable August Evening Hatch

Caddisflies remain important in August because trout can eat them as larvae, pupae, emerging adults, and egg-laying adults. Some Western waters also have a localized late-summer Grannom or Black Caddis event. Exact species and timing vary, but the fishing approach stays practical: cover the bottom earlier, the surface during emergence, and the film during the evening return.

Best August Caddis Flies and Presentations

• Larva or cased caddis: Dead-drift a Holy Grail - Tungsten near the bottom through riffles and seams.
• Emerging or crippled caddis: Fish an X Caddis low in the film. Begin with a dead drift, then add a slight twitch if trout are chasing active adults.
• Adult caddis: Use a CDC Elk Hair Caddis in broken water, along current edges, or anywhere you see splashy rises.

Caddis are more active on the surface than mayflies. A tiny twitch or short skate can trigger a fish, but movement should look like a struggling insect - not a speedboat crossing the pool.

PMDs: A Major Western Summer Mayfly

Pale Morning Duns are among the most important Western mayflies. They are commonly size 14-18 and often emerge from late morning into early afternoon. On spring creeks and tailwaters, trout may feed selectively on PMD nymphs, emergers, duns, or spinners, sometimes switching stages while you are still congratulating yourself for solving the hatch.

When trout are taking adults, use a Hi-Vis PMD in the size that matches the naturals. Its visible post helps in glare and broken current without changing the pale mayfly profile. Fish it with a clean, drag-free drift through the exact lane where a trout has been rising.

If fish are bulging under the surface or refusing the dry, trail a size 16 or 18 CDC Pheasant Tail - Tungsten. The slim mayfly profile and subtle CDC movement make it a strong late-summer dropper when trout are feeding below the surface.

Blue-Winged Olives: Watch the Weather

Blue-Winged Olives can appear across the East, Midwest, and West, and August cold fronts or rainy, overcast periods can bring them back into the conversation. These small mayflies are especially important on tailwaters, spring creeks, and smoother water where trout have time to inspect each fly.

Look for small upright wings on the surface and quiet rises in glides, seams, and foam lines. A size 18 Classic Blue-Winged Olive works when trout are eating higher-riding duns. A size 20 Parachute BWO rides lower and gives the angler a visible post for technical water.

Mayflies usually reward a natural drift. Save the twitching for caddis and terrestrials; let the BWO behave like the delicate, helpless insect it is.

Midges: The Backup Plan That Often Becomes the Main Plan

Midges are available year-round and become especially valuable when August water is low, clear, and heavily pressured. They can matter on tailwaters, spring creeks, slow pools, and stillwaters even when no obvious hatch is visible.

Fish a size 18 or 20 UV Zebra Midge Perdigon as the dropper below a hopper or small dry. Its slim body and tungsten bead help it reach feeding depth without adding much bulk. In clear water, lengthen the leader, reduce unnecessary false casts, and adjust depth before blaming the fly.

August Stillwater Hatches

Lakes and ponds can be excellent August options, especially when freestone rivers are too warm. Watch for Callibaetis mayflies, midges, damselflies, dragonflies, and caddis around weed beds, shallow margins, drop-offs, and wind lanes.

During a mayfly spinner fall, a Foam Case Spinner can cover Callibaetis and other spent mayflies. When insects are mixed or difficult to identify, a small Parachute Adams is a useful general mayfly dry. Fish damsel-style nymphs with slow strips and pauses near vegetation rather than ripping them through open water.

What Is the Best Time of Day to Fly Fish in August?

The best time to fly fish for trout in August is usually early morning, when water temperatures are coolest and Tricos, midges, and mayfly spinners may be active. Evening can also produce caddis and spinner falls, but only if the water has cooled enough for responsible catch-and-release fishing.

• Sunrise to mid-morning: Tricos, midges, spinners, and small nymphs.
• Late morning: PMDs on Western rivers, terrestrials along shaded banks, and dry-dropper fishing.
• Midday: Hoppers and other terrestrials, but only when water temperatures remain safe.
• Evening: Caddisflies, mayfly spinners, and soft-hackle or pupa presentations.
• Overcast or rainy periods: BWOs, PMDs, caddis, and emergers.

Three Proven August Fly Fishing Rigs

1. Hopper-Dropper Rig

Use a buoyant Keller's Hopper or Micro Chubby as the top fly. Trail a small CDC Pheasant Tail or UV Zebra Midge underneath. Adjust the distance between the flies to the depth and current speed. This rig covers bank-feeding trout on top and cautious fish below.

2. Trico Double-Dry Rig

Tie on a visible size 18 Parachute Adams, then trail a black size 18 or 20 Foam Case Spinner. Use the lead fly as a visual reference and focus on a drag-free drift through the feeding lane.

3. Caddis Dry-and-Pupa Rig

Fish an X Caddis or CDC Elk Hair Caddis on top with a Holy Grail - Tungsten below. Dead-drift the rig first. If the hatch becomes active, swing the pupa at the end of the drift and add an occasional controlled twitch to the dry.

August Water Temperature: Know When Not to Fish

Warm water holds less dissolved oxygen, and trout already stressed by heat can have difficulty recovering after release. Many fisheries use about 68 degrees Fahrenheit as a serious caution point, but safe limits vary by species, stream, and local regulation. Carry a thermometer, check current closures, and follow the most conservative local guidance. Trout Unlimited's warm-water guidance is a useful starting point.

Fish early, land trout quickly, keep them in the water, and stop if temperatures are too warm or fish appear sluggish. If the trout water is not safe, move to a colder tributary or higher elevation, try a lake, or switch species. A Superhair Clouser is a good excuse to spend the afternoon chasing bass instead of stressing trout.

What Should Be in an August Fly Box?

Dry Flies

• Foam Case Spinner in black and rusty tones
• Parachute Adams
• Keller's Hopper
• Baby Hopper
• Micro Chubby
• CDC Elk Hair Caddis
• X Caddis
• Hi-Vis PMD
• Classic Blue-Winged Olive

Nymphs and Droppers

• CDC Pheasant Tail - Tungsten
• Holy Grail - Tungsten
• UV Zebra Midge Perdigon
• Small soft hackles, caddis pupae, and drowned terrestrial patterns

FAQ: August Fly Fishing Hatch Guide

What are the best flies for trout in August?

The best August trout flies are usually Trico spinners, hoppers, ants, beetles, caddis dries and pupae, PMD dries and nymphs, small BWOs, midges, and slim mayfly nymphs. Your best choice depends on the region, water type, time of day, and insects actually present.

Are hoppers good for fly fishing in August?

Yes. August is prime hopper season, especially on Western rivers bordered by grass, meadows, and open ranchland. Cast hopper patterns close to banks, undercuts, and wind-blown edges. In the East and Midwest, smaller terrestrials such as ants and beetles may be more consistent.

What time do Tricos hatch in August?

Trico activity usually occurs in the morning. On hot days, female emergence and the spinner fall may happen shortly after sunrise. Cooler mornings can push the best surface activity later. Watch slow pools, glides, tailouts, and soft water below riffles.

What size flies should I use in August?

August often rewards smaller flies. Eastern Tricos may run about size 20-28, while Western Tricos are often around size 18-24. PMDs are commonly size 14-18, BWOs about size 16-22, and caddis frequently size 14-18. Match the insects on your water rather than treating those ranges as fixed rules.

Should I fish dry flies or nymphs in August?

Fish both. Use dries when trout are rising to Tricos, caddis, PMDs, BWOs, or terrestrials. When surface activity slows, trail a small mayfly nymph, caddis pattern, or midge below a buoyant dry. A dry-dropper rig is one of the most versatile August setups.

When is it too warm to fly fish for trout?

There is no single safe temperature for every trout species or fishery, but water near 68 degrees Fahrenheit is widely treated as a serious warning point. Follow local regulations and closures, fish during the coolest part of the day, and stop if the water is too warm or the trout appear stressed.

Final Take: Fish Small Early, Fish the Banks Later

August trout fishing is a timing game. Start the morning with Tricos, spinners, and midges. As the day develops, move toward shaded banks with hoppers and other terrestrials. Watch for PMDs in the West, caddis toward evening, and BWOs when a cool, gray weather window rolls through.

A smart August box does not need every fly ever tied. Carry a visible terrestrial, a precise small spinner, a caddis dry and pupa, a PMD or BWO option, and two dependable droppers. The Keller's Hopper, Foam Case Spinner, CDC Elk Hair Caddis, and UV Zebra Midge Perdigon cover a surprising amount of late-summer water.

Most importantly, carry a thermometer and know when the best decision is to leave the trout alone. Good August fishing starts with reading the water - and respecting what it tells you.

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