It really depends of the movie concept. Sometimes it could be the pivotal point, a demise of a person, or could mean a new beginning to something.
There really is no correct answer to find out what rain represents, but you can tell by the title of just the concept of the movie and get what it represents
After the Rain - film - was created on 2000-01-22.
Purple Rain - film - was created on 1984-07-27.
Represent The Film - 2009 was released on: USA: September 2009
Poison
singing in the rain
The duration of After the Rain - film - is 1.52 hours.
November Rain - film - was created in 2006.
After the Rain - film - was created on 2000-01-22.
The duration of Let It Rain - film - is 1.17 hours.
The duration of Purple Rain - film - is 1.85 hours.
The duration of Hard Rain - film - is 1.62 hours.
Let It Rain - film - was created on 1927-02-12.
Hard Rain - film - was created on 1998-01-16.
Purple Rain - film - was created on 1984-07-27.
Represent The Film - 2009 was released on: USA: September 2009
The 1999 japanese film 'After the Rain' was directed by Takashi Koizumi. You can read more about this film online from the Internet Movie Database website.
His second film was The Devil's Rain.