I like to fish in the winter. Less people, more wildlife, awesome scenery, and often great fishing. I'm on the Eastside (of the cascades), and agree with what others have said. If the daytime high is below 30, not really worth it with the guides freezing up the entire day. But, 30 and over I am game!
Feet: 1 pair snowboard socks under 1 pair thick merino wool. Don't wear so many socks your boots are tight, that will make it worse as
@flybill pointed out.
Legs: 1 pair fleece long John's, under 1 pair fleece sweats, under 1 more larger pair fleece sweats, and of course, under your waders.
Top: I like the 511 stuff for base layer (can be found at Cabelas). I wear a mock turtleneck with nothing under it. Then a fleece pull over, then a fleece lined hoody, and then my Simms poofy gold insulated or whatever.
Head (super important): I wear a hat or beanie, but either way, you need a Buff that covers your ears and comes up over your hat (some like fleece lined buffs but i find them a little snug). Make sure your ears are covered, and when you don't need peripheral vision use your hood on your jacket.
This set up keeps me warm. I don't wear gloves, as I can't stand trying to tie knots in them, or taking them on and off to tie knots, or manage line. Sometimes if it's really cold I'll throw gloves on while I am rowing but not a huge fan of that either. Hand warmers in the pockets of your waders are fine, but they never work that great without O2, and with all the layers, my waders end up being snug, haha!
Lots of great winter opportunities out there, and dressing appropriately can help you enjoy them. You're never going to be perfectly warm, but sometimes the struggle is worth the reward. A Flask can help, as well as some company! Get out there and enjoy!!!