quite true rain does come from the sky, but you would have to be a bit daft , not to get the guist of my meaning, also within that water flowing over the gutters or other outlets is , dead birds , seagull shit and toxic pidgeon crap, and if humans have access to a roof area or a dormer window , i will let you think what else is laying about up there, 8 pints and a curry gone wrong , comes to mind.