A glacier-fed river keeps a schedule, and most of us fish it as if it doesn’t. The same run that shows fifteen inches of visibility at first light will show six by two in the afternoon, because the snow and ice feeding it melt hardest when the sun is highest. That single fact reorders everything about how you pick a summer steelhead fly: not by the hatch, not by your confidence pattern, but by how much the fish can see at the hour you’re standing there. Get the clarity cycle right and the fly almost picks itself.

This is a different problem from the one most swing anglers learned on. MidCurrent’s winter and early-spring color guide deals with rain-driven mud on cold water — turbidity that arrives at random after a storm and clears on its own timetable. Glacial summer turbidity is the opposite kind of animal. It’s solar-driven, it’s on a near-daily clock, and it shows up warm. Understanding that clock, and what it does to a fish’s eyes, is most of the game.