After a few days of hot, humid days and nights, a recent dawn broke with chilled air and cold rain, influencing me to wear a heavy fall jacket to walk our 12-week-old yellow Lab.

This minor incident reminded me of a truth about summer salmonid fishing in Maine’s rivers and large streams. In our northern state, unseasonable weather proves common enough and lowers water temperatures, which spur angling action, particularly in northern destinations such as in the Rangeley, Moosehead, Baxter and Allagash regions.

Such meteorological events draw trout and salmon from ponds and lakes, and into flowing waters. Sometimes these brief cold snaps and heavy rain occur the day following a blistering, humid stretch, but anglers don’t react overnight to the improved fishing. However, fly rodders and hardware casters who do hit rivers immediately after water cools can have long stretches of superb fishing on blue-ribbon rivers. Storied places such as Kennebago River in Rangeley, East Outlet of the Kennebec River in Moosehead or Nesowadnehunk Stream in Baxter can offer fishing bonanzas in midsummer to those who persevere.

IFW research indicates that Maine salmonids can migrate with great speed. Data from a well-known study showed that fisheries biologists on Messalonskee Lake had captured and released a fish that swam south down that lake, west and north up a long stretch of Belgrade Stream and north through Long Pond’s first and second basins, before arriving and being recaptured 24 hours later where The Spillway empties into the pond.

When cold air and rain fall in summer, wise anglers fish near river mouths not far from lakes and ponds to cast to trout and salmon just entering flowing water, but plenty of exceptions exist, where salmonids move far upstream from river mouths – as the study showed.

Here’s an example of a quick migration of miles: Brook trout in the Rangeley region’s Cupsuptic Lake may enter Cupsuptic River and beat it upstream through many rapids to Big Falls miles away. In summer I’ve caught brook trout at this Falls a day or so after a cold rain, and my trip often passed in solitude with no company.

In early spring, baitfish flies and lures that match prevalent baitfish work like gangbusters, but in summer invertebrate imitations may produce better. Sacrificing a fish for a stomach autopsy can provide folks with examples of exactly what constitutes the menu that day.

Years ago I used a simple, hand-held gadget that sucked food from live fish stomachs, a tool that eventually received bad press for allegedly killing fish. Once, a man on the Sheepscot in Somerville severely criticized me for using this tool because of that reason. This “match-the-hatch” invention might have been injurious at times, but back in the day when I used one, I’ve caught salmonids with identifiable marks, sucked food from their stomachs and landed them again in following days. More importantly, dispatching a fish for an autopsy kills the fish every time, but the hand-held, food-retrieval device ensures survival for some specimens.

When I fish a river often, though, I usually know what they’re eating because of catching them on certain flies trip after trip. In fact, 30 years ago or more, my tool for extracting food from fish stomachs broke and I never replaced it.

In Maine’s gravel-bottomed rivers during late July, August and September, blue-winged olives (BWOs) hatch between 10 a.m. and noon, or 2 p.m. to around 3 p.m. (depending on species) and offer fast fishing to folks who match the size (often ranging from size 18 to 24 hooks). Lots of waterways produce BWO hatches now through September.

If a water has BWOs, then a pheasant tail in size 18 to 24 produces during the 30- to 45-minute period before the hatch, because that dark pattern matches the swimming larvae. I often stick with a size 18 nymph because a size 24 – slender to begin with – look ridiculously diminutive.

Many BWO species are swimmers as opposed to clingers, crawlers or burrowers, so a good presentation includes casting quartering across and downstream, letting the fly swing in a tight arc and then retrieving it by rolling line over the fingers to simulate a nymph swimming upstream.

I also like size 18 to 24 cream, upwing dry flies to imitate prevalent summer mayflies, and the same size and color with down-wings and no tails for caddis hatches. Rust-bodied or tan caddis nymphs with slate wings flush against the body, a gold bead-head Hare’s Ears, gold bead-head Prince, god-bead-head Zug Bug and similar choices take fish now, often on dead-drift presentations. Small sizes work in the depths of summer.

Keeping a close eye of weather reports for those cold spells that most folks complain about can get anglers into fun fishing in solitude this month.

Ken Allen of Belgrade Lakes, a writer, editor and photographer, may be reached at

[email protected]

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