Originally Posted by
leaftye
How long do you plan to take during breaks and outside your sleeping bag at camp? If that will be very little time, then you don't need much to stay warm because you'll be generating lots of heat while hiking. What can still defeat that is (1) wind, (2) rain and (3) not walking fast enough. Wind is easily handled by a very lightweight wind shirt or thicker nylon shirt, and that can take you into sub-freezing temperatures. I don't have much experience with rain, so I can't help you much there, but I can tell you that you'll probably sweat more than any truly waterproof membrane can handle. Not walking fast enough can be caused by creek crossings, terrain including rocks and snow, and sometimes altitude. Those limit how much heat your body can generate.