Yeah it should keep you warm, i wair it over under armor and below my ski jacket and stay toasty. At least in the 10-15 degree and up

Adam, I guess it all depends on how cold natured you may or may not be. I am not very cold natured and I own the TNF Chesterson Crew, which is very similar to this item only it doesnt have the upper neck band (which should help in cold temps) and it also doesn't have the zip. I wore my Chesterson under my Montbel UL Down Parka without a base layer under the fleece in single digits with wind gusts from 15-30 mph (and many of those days were sustained winds making the actual temp seem more like a lil under 0). However, as already stated, I am not a cold natured person so it does me just fine. if you're not that cold natured I would imagine this shirt would fair well especially with a base layer and a good shell to go over it. Icebreaker may be a good one to look into; I have no experience with those, but hear good things about them. regardless, this is not a bad deal for this shirt. I am actually looking at one for myself cuz my Chesterton doesn't have a front zip to dump heat when I'm really active. Give it a shot and if it don't work out send it back to BC for a refund. You can't go wrong with a BC test drive!