Lightning and Rain add incredible atmosphere to a level.

Place NATURALLIGHTNING sprites (#4890) tagged [Channel,0] in areas where you want lightning to randomly strike. Place an S[Channel,28] in every sector containing a lightning bolt (this ensures that every sector flashes in response to the lightning). Use WATERDRIP (#660) sprites for raindrops. It's important that you place WATERDRIP sprites on the ceiling, otherwise they'll be virtually intangible. Just point the mouse cursor at the ceiling, press S, then change the new sprite to a WATERDRIP. Adjust its palette value to 13, and make it as transparent as you wish (with T). Giving the WATERDRIP sprite a Hi-Tag value greater than 0 will disable the dripping sound effect (if you would prefer to use only the ambient sound instead). You can then copy and paste the raindrop from there. For realism, texture the floor with an animated raindrop texture (#5065, #5068). The final step is to place an M[AudibleRadius,358] for the ambient rain sound effects. For AudibleRadius, a value of 1024 is equal to the largest grid square.