Ive back-pack hunted for elk in Colorado for decades, temps range from the 80F down to -20F on very rare occasions.
youll find early season archery ,far warmer than third rifle season up at 10,000 plus feet elevation.
now you should obviously consider what you NEED to stay reasonably comfortable under the likely conditions you'll see.
one of the most miserable nights I ever spent was the first night I camped in the California Warner wilderness, temps dropped to -5F
I had a SEARS sleeping bag rated for 10F and even wearing a parka and sweater inside the bag I felt like I was freezing to death,sleeping in the tent.
light weights great, but the object of having a sleeping bag is to allow you to stay at least semi-warm while you sleep.
now having a good insulating pad under the bag helps and having a pull over face mask to restrict heat loss from your head and face helps,but think thru your choices based on the likely conditions and don,t get mesmerized by light weight or low price alone, your life could depend on staying warm and dry.
down in the 600-800 loft range is effective and light weight, but if it gets soaked with water its nearly useless a roomy gortex outer bags helpful.
get a bag thats a bit too heavy or bulky its a P.I.T.A. to carry and pack, but you might prefer that over FREEZING TO DEATH with a soaking wet, useless 2 lb down bag if your forced, to use it because you got soaked , accidentally falling in some creek covered with ice,or caught hiking far from cover in a down pour in mid 30F temps where a good synthetic bag might provide far more warmth.
http://www.backpackgeartest.org/reviews/Sleep%20Gear/Sleeping%20Bags/http://www.outdoorgearlab.com/Backpacking-Sleeping-Bag-Reviewsyeah Im sure Ill get flack over this but I found this bag and pad, and gore tex outer bag a decent choice, yeah, I generally use these only if I,m sure to see sub zero temps and the bag alone over a tarp works fine on most hunts but I keep the other two components in the truck along with a good pack frame and two man tent.
http://www.rei.com/product/828210/the-north-face-inferno-20-sleeping-bag#specsTabhttp://www.mpgear.com/item/astroinsulated/Nemo-Equipment-Astro-Insulated-Sleeping-Pad/1.htmlhttp://www.amazon.com/Military-Surplus-Bivy-Sleeping-Cover/dp/B00276IGM4
