Allright, I've just completed the developing and texturing phase of my map, and so now only the further detailing phase remains. For those who want to see what I did for the last four hours in texturing phase, here are some pics. I fixed those two nodraw errors after noticing in this image. Getting back to the point, I'd like the atmosphere to be during a dark and stormy night, and to pull that off I'd need actual rain. So how do I do this?