Originally posted by Aesthier:

Console Commands:
env clear = clean air
env -1 = resets environment back to system defaults.

That should do nicely thanks. And thanks for all the comments. Perhaps it might be because I use mods. Which does have a remove fog command but it doesn't work and renders console commands not to work in game. But it does seem everytime I am going to build something the bank of fog suddenly appears and when I say thick I cannot place one stone on top of the other as visibility is 0 .