This is because the material itself is weatherproof, however the ink printed on it is typically not. Most inkjet printers work by laying the ink down on top of the label surface, meaning the ink does not soak through or become embedded into the material. This means the ink can still be affected by water after it dries. To protect your prints, we recommend applying a top coat to your label to act as a seal against water and keep the ink from running when wet.