February 3rd, 2016, 15:12
Now that I had my fun, I will cease to be a wise*ss. I was told that in order to see rain, you need to go into your display settings and make sure they are high enough to support rain being displayed. (More than likely, they need to be maxed out)
Aside from thunderstorms, if you want different types of cloud decks / rain, you need to go into advanced weather, which you can do in either Quick Combat or Free Flight.
The second part of your question is that in order to include specific weather in missions, you need to create the weather in free flight, and then exit the sim after loading free flight or quick combat. The weather information will be stored in a specific area of the cfs2.cfg file. Then, you need to open up the mission file, and copy and paste the weather...