Higher chance of fog

[birgirfg]

For my survival mode playthrough I was thinking of making the world have more of a dead atmosphere, and I get that feeling most when there is heavy fog weather. My question is then, is there a way to make the fog weather the most common weather? Or add a slight bit of fog to some other weathers?

If this is easy to do I can do it myself, someone just has to tell me how. :D

(I'm using True Storms mod)