I will REALLY 2nd what Dirt2 said. I have had temps below 10 degrees every year I have been pack hunting. I always bring a - 30 degree bag and have been happy to carry the extra weight. Last year a friend went with me to hunt grouse and brought a 0 degree bag. He was pretty useless when the temps did get into the 60s later each day. He bought a - 30 degree bag when he got back... By the way, Cabelas is closing out those bags now. They are top notch and 50% off, going for $99 I think.
http://www.cabelas.com/cabelas/en/templates/product/horizontal-item.jhtml?id=0006792513498a&navAction=push&am p;navCount=2&indexId=cat20144&podId=000679 2&catalogCode=OF&parentId=cat20144&par entType=index&rid=&cmCat=MainCatcat20075&a mp;hasJS=true
Good Luck,
CE