Very warm - kept me warm enough - almost to warm even in below freezing temps (well below) while on a whale watching open air speed boat going 25+ mph.  Actually the top of my head was a little sweaty when I took it off at the end of the trip.  Didn't use the thin little piece that was the mouth and nose cover though -- instead I was using a Polartec Fleece Neck Gaitor to protect those areas.