Cardboard boxes are a desirable recyclable and should be set out for curbside recycling whenever possible. But what happens if Mother Nature has other plans and rains on your cardboard recycling parade? When cardboard boxes get wet, you should not recycle them. When the fibers are saturated with water, it weakens them and reduces the quality of the recyclable. Instead, place wet cardboard in a dry place and let it dry out before returning it outside for recycling.