Do clouds block UV rays?

According to the Doctors of Optometry Facebook page, UV rays are so strong, up to 90% of rays can penetrate through the clouds. They can also reflect off surfaces such as sand, snow and water. No matter the day, always protect your eyes from invisible UV rays.

A significant amount of UV rays can actually enter your eyes even you are wearing UV blocking eyeglasses.  That's because those glasses block the UV rays that come at them from the front but UV rays can reflect of the back of the lens (the side of the lens that is closest to your eye) and into your eyes.  To stop that, you should wear advanced UV protection lenses with an ESPF (eye-sun-protection factor) of 25 or higher.

Learn more here.