I'll add that with a pack that fits close to the body, it can be HOT in the summer- I like my body to breathe. However, I went from a Performance Lobo-style pack to a Hydrapak (dont know the model offhand) that has four contact points with the back but allows airflow between you and the pack. I never feel overheated with it. Of course, in the winter, a snug pack w/ hot coffee under a parka can feel good!