Rain symbolizes multiple things depending on the context in which it appears, but most commonly connotes sadness, rejection or despair. Because rain diminishes sunlight, it creates human emotions of darkness and depression. Rain is often used metaphorically in literature to represent discontent or to invoke a forlorn mood. Many films use rainfall to create heightened drama and a sense of foreboding, symbolizing human tears.
In Ernest Hemingway's "A Farewell to Arms," rain appears throughout the novel and symbolizes the unhappiness that the characters experience due to inevitable events in their lives. Falling rain occurs during passages in the book when the characters are anxious and feel a sense of loss and doom. For example, after his beloved's death, the story's protagonist leaves the hospital and walks home in the rain.
Because rain is a common natural occurrence vital for life, rainfall can also represent rebirth and emotional cleansing. In some geographical areas where rain is not abundant, rainfall is cause for emotional relief and happiness.
As explained in Psychology Today, symbols are often multifaceted and therefore cannot be held to a single interpretation. Symbols are often powerful because they have many layers of significance that cannot be fully understood or captured in words.