Wearing a white shirt on a hot sunny day is generally cooler than wearing a black shirt due to the way different colors absorb and reflect sunlight. White and other light colors reflect most of the sunlight that hits them, while black absorbs a significant amount of that light.
When sunlight strikes a black shirt, the fabric absorbs more solar energy, which causes the shirt to heat up and, in turn, makes you feel warmer. This process can lead to discomfort in hot weather, as the absorbed heat can transfer to your body, raising your overall temperature.
In contrast, a white shirt reflects a larger portion of the sunlight, keeping it cooler. This reflection helps maintain a lower temperature on the surface of the fabric, allowing you to feel more comfortable even in high heat conditions. Thus, choosing light-colored clothing can be a simple and effective way to stay cooler and more comfortable during hot summer days.