The weather engine is already implemented, but not activated, that's why many textures do not get used. However, SKY-d1 is used for day in non-Desert and SKY_d7 in desert environment, while Fog and Sandstorm are used for foggy weather in non-desert and sandstorm for "foggy" weather in desert terrain. These foggy textures are used when you switch visibility to below 500m. Knowing these fileneame, you can manually replace them, and acchieve visual effects like to be seen here:
I use some replacements from that package
http://www.steelbeasts.com/modules.p...=getit&lid=940
myself, but not all, many of them are having to high colour saturation.
Resolution: 800, 1024, 1280 are the most used.