The main attack takes place at night, I think to create the right look and some contrast in the shots it probably makes sense to make the night sky black/dark. I just positioned some set elements in the backgrounds of the shots to create this as the scene is already being lit using a 'sky' object.
I need to test out the renders with this night sky in photoshop layed up with the texture and experiment with blend modes to get a nice look that fits in with the rest of the shots.