Cotton is known for it's cooling properties. Wear a cotton shirt on a warm day and your skin will still be able to breath and keep cool. A cotton shirt will also take moisture away from the skin, which is another factor in keeping you cool and dry feeling in the summer months or when the heat is on (in more ways than one) at work. Similarly, cotton is a natural insulator and so as well as being a breathable fabric that will keep you feeling cooler, more so than most other synthetic fabrics out there.