Sleeves are definitely out of the question when you're running in the heat, but if you're looking to get even airier than that reach for the Icebreaker Kinetica Sleeveless Crewe Top. It's made with a lightweight, breathable, and quick-drying fabric that'll keep you comfortable as work out in warm weather, and features a full mesh back to turn up the cooling factor even further. The fabric, called Cool-Lite, is made using Tencel and merino-wool fibers, so you can have natural moisture wicking and temperature regulation as you sweat. The back is constructed fully with eyelet mesh to enhance airflow on long runs, and the relaxed fit moves freely with you for uninhibited movement and comfort. The crew neck design ensures that it won't move around too much as you run, while the natural odor-fighting performance of merino wool has you covered during your longest and sweatiest runs.