My favorite lake is at 3200 ft elevation and as the surface water rises in the summer to around 68F, the trout go deeper as shown on my Humminbird sonar......in the 25 to 70 foot depth seeking colder/cooler water.
I use a down rigger and no flashers....just troll a 3" to 5" size flat fish, Quickfish or #6 silver blade spinner with a silver/blue body, about 75 feet behind my PA-14......this is not an unusual sized trout I bag......9# 13 oz, 29" long Rainbow.
A couple of summers back in early June, I hooked a 8.5# Rainbow on a "Wedding Ring" lure in 9' of water....at first I thought I had hooked a tree stump, but "the stump all of a sudden began to move"!