Cooling Yellowstone flows set up a fall brown trout push

What's biting

What's next

Expect the gradual fall recession to continue as irrigation withdrawals taper off for the season, the typical pattern for this drainage in late September, with water temps likely easing further toward the upper 40s over the next several days if the current trend holds.

Low light matters more now than midday. Plan around dawn and dusk windows, and use the waning gibbous moon's overnight feeding activity to your advantage on early starts. With flows still moderate and clarity holding, this weekend is a solid window before conditions tighten further into true fall.

Context

Late September sits at the front edge of the fall transition for Yellowstone and Snake River tributaries. Water in the low 50s and easing flows are on schedule for this point in the season, as summer irrigation demand tapers and rivers settle into a more stable base-flow pattern. This is the stretch when brown trout begin keying harder on baitfish ahead of their October–November spawn, a shift that typically holds through the first hard frosts.