Rain paper is a type of paper designed to be written on when wet. It is usually made of a special material that is waterproof, allowing the ink to stay on the paper and not run off. The paper is usually white or transparent and can be purchased in various sizes. It is often used by outdoor enthusiasts such as hikers and campers, as well as by emergency responders. Writing on rain paper is a great way to record information in wet conditions and is often used in emergency situations where traditional paper may not be available.