Hello ! A long time ago Beamng Dev talk about rain : http://blog.beamng.com/blog/page/11/ There was a mod, but he never been release, So, why we never get this rain in the game, It's still in project or it's dead ?
You can activate it. Go to the world editor library- level- envirorment and then preticipation. (should be spelled correct
You're doing it wrong. Rain still works fine, try JRI. It has the rain in by default. Just turn up the "NumDrops" to 1024 to see it.