During the brutal summer days long sleeves are good to protect your skin from the sun. If you wear a loose cotton shirt under an evaporative cooling vest, the water will evaporate and cool you off. loose cotton is key, White (and warm colors) reflect heat, versus black (and cool colors) which absorb heat. Ideally, you want something like a white, cotton button down. The sleeves will block the sun from burning your arms, and the Vest allows ample airflow, cooling you down immensely. Keeping the evaporative vest moist will keep you from sweating and using your body’s precious hydration. You will actually feel cooler wearing a loose, white, cotton button down than wearing a dark T-Shirt in the summer.