"It's Raining Again" is a song recorded by British progressive rock band Supertramp and released as a single from their 1982 album ... Famous Last Words ... with credits given to Rick Davies and Roger Hodgson, although as indicated on the album sleeve, it is a Hodgson composition. The end of the song incorporates the old nursery rhyme "It's Raining, It's Pouring".

Answer this question: who sings the song it's raining again? Let's give stream of consciousness first:
The important part for answering this question is: "It's Raining Again" is a song recorded by British progressive rock band Supertramp and released as a single from their 1982 album ... Famous Last Words ... with credits given to Rick Davies and Roger Hodgson, although as indicated on the album sleeve, it is a Hodgson composition.
So, the final answer is Supertramp.