Been working on this today, I am far beyond proud of it! This is also my first successful 1080p upload, so do it the justice it deserves 
I’m using my own shader code to generate the clouds, a custom sky sphere with 3 UV channels. The Blueprint is a modified version of Epic’s starting sky. I didn’t like the way the clouds rotate in a circle, but it’s incredibly hard to get the effect of ‘flatness’ on the sky using a sphere. A couple of flukes in the material editor and I seemed to be able to pull it off.
The whole sky is only 2 texture samplers, and around 163 instructions IIRC. There is also functionality to render a moon disc (which also lights and shades the clouds), and stars. Stars aren’t too great right now so I’ll show those later. In the meantime, does anybody (e.g., from epic) know how Gears of War 3 managed to render a texture for it’s moon and use it as the light source in Gears of War 3? I’m struggling to find a way to map it to the sky dome and offset it by the camera vector. if anybody from Epic could help me on this I’d appreciate it!
I need to figure out how to offset the star texture so that it looks like it sits ‘behind’ the sun, right now they’re just mapped to the skydome which looks incredibly strange when you have a moon disc rendering further away than the stars. Need some clever camera vector magic…