Timelapse of my current 3D space implementing my proce55ing originated weather simulator. These are motivated by a combination of heat, water, moisture, and terrain, _not_ a run of the mill noise filter:

I now "know" when a given area will have rain, if it's hot or cold, if it's humid or dry. These basic clouds are just to check and see if the simulation is working - there's a ton of ways I can visualize this stuff. There's also quite a number of ways an agent or player could theoretically interact with or be affected by it...
Took a very simple take on how to do day and night cycles here:
http://www.phys.uu.nl/~0307467/docs/skydomes.htm
and applied it to the sprawling sky I currently have in my codebase.



I decided to plan for specific day/dusk/night "fog" colors as well as light colors, interpolated based on the height of the sun. Actually, any star - With this setup changing sky color, sun color (and hence, what sort of of light hits the planet), and the like are trivial to change now.
With a star/sun height calculable, along with seasonal variation, I'm already working on getting my previous weather simulation code working within this space. That implicitly means I'll have data for clouds, fog, rain, and vegetation cover acting dynamically over a virtual globe - although how I visualize these things is a separate problem that has many solutions.