My first trip with this bag was on a 5 day backcountry hiking trip in Killarney between Christmas and New Years. The bag's performance was adequate down to -17oC (ca 0oF), which was good considering I was often pitched directly on rocky surfaces. Lower temperatures would undoubtedly be tolerable if camped on a more insulating surface. The zipper-line is clearly the cold point of the bag but can be avoided with practice. The accompanying compression bag is a nice addition to the "kit", but is unfortunately poorly constructed... Restitching the anchoring sites of its straps is ESSENTIAL before using it on a trip.