Ren_Mem gives sage advice when he suggests you use the four-pane view for assembly.  You can see exactly where something is in the scene if you can see it from top, left and front, as opposed to just from the rendering camera's point of view. 

You can area render from any of the non-ortho views, as well, so you'll see exactly where, within the volumetric cloud's bounding box the cloud itself exists.