When fall water drops into the 40s, two things about the swing have to change: you slow the fly down, and you get it deeper, to the level where the fish are holding. The water temperature sets speed and depth; its clarity and the light set fly size and color.

Steelhead are sea-run or lake-run rainbow trout, and by fall the fresh ones are entering the rivers in their best condition of the year: chrome, un-pressured, still carrying the aggression of a summer of feeding at sea or in the lake. They are also cold-blooded, so they slow down as the water cools. A fish that would chase a fly several feet in September holds tighter in November, and you have to bring the fly to it. On the Deschutes, the Pacific Northwest’s home water for swinging, the river runs about 58–65°F in September and cools through the 50s in October, its most productive month; the drop past 45°F usually comes in late fall.