What are some examples of how rain is used as a symbol in literature through short stories or movies or novels?
Used to create a depressing or unsettling mood.
Many gothic novels use rain (and other forms of dull weather) to create an unsettling mood, and sometimes even the feelings of a character (known as pathetic fallacy). This is effective as it a simple way to convey emotions through a text.
It can even create tension as seen on the way to the Lyceum Theatre in Conan Doyle's the "Sign of Four". On the way, Watson uses the depressing features of a Victorian London background to convey a sense of tension as they make their way towards the theatre in search of a mystery.