I just got back from a 3 week road trip through the western US - camping, hiking. I wore the Nano in many different situations, from mountains to high desert. The coldest temp on the trip was in the 20's and wearing the Nano with a primaloft vest and long sleeved t-shirt I was comfortable. Eastern Sierras was cool and windy but never a problem with this jacket. Even spilled a cup of coffee on it one morning but wiped right off and no staining. Perfect jacket to always have handy in your day pack, besides it's cozy. I'm 5'11' 170 lbs and the large is a great fit with room for layering.