Putah Creek in Northern California is a great winter fishery. But, make sure you don't fish on the redds (where the fish are spawning). Otherwise, enjoy catching big Rainbows and if you're lucky you'll catch a monster Brown.
Here's a big buck I caught a few years ago on the creek. It took an olive bead head Woolley Bugger. Honestly, I can't believe I actually landed this fish. It was massive! And, no, it wasn't a Steelhead or a Salmon. It was a Rainbow.
Don't stop fishing just because it's fall and winter is on the way. Just get your warm clothes out and find some fish.