If you have to carry it then the weight is a factor. I use a 1# 6oz bag rated a 30 degrees and have used it Sept/Oct in Wyoming. Definately not warm enough sometimes so on come the socks, long underwear, balaclava, and puffy jacket as needed to be warm. Any clothing that you can comfortably sleep in can up the rating of your bag. None of the items are extras therefore you save weight on your sleeping system.