Lake fishing in late summer can be at its best in the low light hours of early morning or late evening. During these periods, many fish can still be found roaming the shallows, making them easily accessible for a fly rod. Most any surface fly or slow sinking offerings can be effective during these times. Cover as much water as possible looking for those cruising fish in the shallows looking for a meal. Once the sun is high in the sky, you will need to concentrate on cover providing shade lines, or take your presentations deeper.
River fishing for trout can get tough in late summer unless you go in search of wild fish in the highest elevations, or capitalize on boosts to river levels after rains. Terrestrial patterns and attractor dry fly patterns work well this time of year. Stick with a dry fly/dropper combo for the small pocket water in high elevations and keep moving. Buggy nymphs and worm patterns also excel after a heavy rain.