“UV rays can pass through thin, light-colored, and loosely woven fabrics. For optimum protection, wear tightly woven, dark-colored, long-sleeved shirts and pants, as well as wide-brimmed hats. Certain types of fibers also provide more protection than others. "
https://www.healthline.com/health/skin-cancer-protection/sun-protective-clothing#:~:text=UV%20rays%20can%20pass%20through,provide%20more%20protection%20than%20others.
Be aware that covering up doesn't block out all UV rays. If you can see light through a fabric, UV rays can get through, too. "