How much impact will weather effects have on game play?

[eMaGyN]

I know in previous games it is possible to be hit by lightning. I was wondering if the battle field will be greatly effected by weather conditions or if they are being implemented at all. What i think would be really cool would be if the weather is rainy there be a slight fog, the heaviest of fog near areas of water and such... i just thought it would add to the realism