When the summer sun comes calling, the Arc’teryx Accelero is the runner’s answer. Super-thin polyester panels across the shoulders and back increase airflow. The fine fabric comes in handy while wearing a pack, drying sweat almost as quickly as it can accumulate, without forfeiting comfort. The flatlocked seams are also placed specifically to avoid chafing, while the reflective detailing will keep cars, night cyclists, and the occasional deer from running you down from behind.