have a setting in game creation where the fog state rotates (or moves like in real life). One turn it is extreme fog (foggy day) and another day it clears up and everyone can see for one turn. Another day could be a slew of Recon cards spots (spotty day). It would be on a randomizer so you wouldn't know what type you got. You could also set a default fog level so that you can have a base to go off of.
Gavin Garrett commented
In addition, there could even be fog in different parts of the map.