The only truely cold weather hunting iv'e done has been up in Canada, and i'll admit i was worried about sitting all day in subzero conditions with no heat. I knew our first day was going to be about 15 below warming to 5 below. I had a heavy set of bibs, a heavy parka, boot blankets, and a heavy facemask. Plenty of handwarmers too. I also had one of those heeter body suits, not that brand but the same concept. I decided that if i got cold i'd put the body suit on or walk the trail back and forth till i got warmed up. I was hunting in the woods, sitting in a shanty, so wind wasn't a problem. Turned out i never need my body suit or had to walk to keep warm, i was pleasently surprised. Also sitting in that shanty i could move around a little without worry so that helped. Also we were gun hunting. Ended up that hunting under those conditions ended up being a big part of why enjoy hunting up there, more of an added challange from the elements to deal with i guess.
I'm not sure i could do bowhunting in a tree stand under those conditions.