Connie - you are dead right about it being Douglas Adams - can't remember which book of the trilogy he appeared in - the fifth, I think (Mostly Harmless)

The lorry driver was, in fact and unbeknownst to himself, a rain god. He eventually realised his potential and made a fortune selling his services to third-world countries stricken with drought.


EDIT
No - it isn't Mostly Harmless - try Goodbye - and thanks for all the fish, which is the fourth book.