Can't see it being called off. The Emirates has a good undersoil heating and drainage system, the trains at the moment where I am (South east London) are fine, although obviously that could change, stadium isn't really in a flood-exposing area and the rain at the moment isn't that heavy, just very persistent. Although it might be different in North London, its hardly apocalyptic here, not like before West Ham at home in 2010/11. Games have gone on in far worse than this.