If you’re fishing for browns, that’s the best time of the year. Not just my opinion, that is pretty well the common knowledge around here. I live in Livingston, where the Yellowstone flows through about 50miles north of the park. The Yellowstone and it’s tributaries are ripe for streamer action in October.
Almost all of the alpine lakes are full of cutthroats, which are spring spawners, but if you’re willing to get up there, they aren’t as picky as you would think. Buggers, chubbys, stimulators, nymphs. Bring a selection, you’ll find something that works. Keep in mind it’ll often start snowing here in Sept, especially up high.
The Yellowstone is more easily fished by raft or drift boat, and at that time, you just pound the banks with big, articulated streamers, or the biggest bugger or streamer you’ve got. Black, olive, or anything that looks like a fish (sorta). This is the funnest fishing on earth. I use a 7weight with full sinking line, but a 5 or 6 will work if that’s all you got. There’s a bunch of river access, but wading through Yellowstone is tricky at best, and deadly at worst. Look for the named fishing access signs along the roads.
If you want a day in a boat on the Yellowstone, Sweetwater, Dan Bailey, and George Anderson’s are all excellent guide services here in Livingston. I’ve never hired a guide, but I think it runs $450 and up a day plus gratuity. With the guys I know who are guides, this is well worth the $
The tributaries and creeks are equally great at this time of year with streamers, most have at least some access, and some have great access. Use the same patterns for spawning browns; big ass streamers.
Montana has a great river access law, familiarize yourself with this great portion of our MT Constitution. An OnX subscription can be a great aid in accessing some spots too.
There’s a ton of great cutthroat, brook, and rainbow trout fishing here.......but October is for big browns.
