For the past three Octobers that I remember for sure, we had massive snow falls in the middle of October (then melted quickly). This year, there have been a few days that made us feel "the chilly weather is coming" but it's been warm over all - the latest weather forecast suggests it goes on through this week (then supposedly cool down quite a bit).
Typically I have some guide trips in October but also this is the time for me to fish for my own.
Perhaps the Atlantic salmon gear, imported from UK, wouldn't be required on the Yellowstone River. However, one can always daydream of the hollowed Salmo Salar (Atlantic salmon) and enjoy practicing the Spey casting with its cousin Salmo Trutta (brown trout). Actually this specimen put some fight against the overpowering gear (of mine) and pulled some lines out of my Bougle!!
As for the spring creeks, good actions continue since "after the flood", really.
Believe it or not, you might still encounter PMD, yes, PMD.
Overcast days were preferred for the fall baetis hatches but even on the sunny days certain amount of baetis will hatch and the midges will always offer you some challenging fishing.
So enjoy the fall while it's warm (and when it cools down)!!