霖 Lín is composed of the 雨 radical on top and 林 (Lín) "Forest" on the bottom. 林 (Lín) "Forest" is the phonetic component of 霖 (Lín) and is written with two 木 (Mù) "Tree, Wood" because a forest is composed of more than one tree.
霖 can be remembered as a continuous heavy rain feeding the plant and animal life of the forest.