I just spent the night out in my new snugpak elite 4 sleeping bag rated comfortable -10°c. I used a spacious bivi bag and a decent thermarest mat. I wore a moreno wool base layer and a hat. I had a tarp set up as standard A over me. The grpund was already soaking. I went to bed warmish. There was a extremely light wind blowing across me. It rained all night but I remained perfectly dry and no condensation inside bivi bag in the morning. Overnight lows were only +5°c. I wasn't exactly cold but not super warm either. I certainly didn't feel like I would be comfortable at -10°c, the bags comfort rating. Am I missing something? (Nb I sleep at home with the window open and no heating on in bedroom).