I went elk hunting 2 years ago in Colorado. I left on the 8th, and was gone until the 17th. We were up in the mountains. During the day I wore short sleeved shirts, and just regular, light weight pants. Come night time though, We were all in long johns, and tucked deep in our sleeping bags. The mornings were chilly also. Carry a good backpack so you can shed clothes. Have fun!