It can get hot during the day on a summer or fall hike. To avoid massive back sweat while you're clambering up the trail, Lowe Alpine made the AirZone Centro 27 Pack with a ridiculously airy back panel and an adjustable torso for a precise fit. While this back panel has minimal contact with your back, it still provides plenty of support for snacks, a wind jacket, and a water-bladder. A front stash pocket keeps sunscreen and trail maps at the ready, while a large side mesh pocket holds your water bottle.