Slitherine

Except soft ground, is there other things which can be added to similate impact of weather during battle?

For instance FOG which reduce visibility , mud and snow movement, heavy rain for shooting Etc...

Is someone create a board for forecast impact?

I believe snow and rain cause a shooter to be disordered for shooting only. You could add in LOS restrictions I suppose if you wanted to. Would allow for Nappy to sneak up on the Austro-Russians from low lying fog at Austerlitz.

sound good for shooting, concerning Fog may be reduce LOS to 6MU could be interesting.
For movement with mud or snow I'm still balancing between reduce by half or by 2MU.

I suggest 2 MU as all troop types are going to be affected and I doubt you can move any faster in column in mud than you could in line. Artillery would likely be really slow as the wheels tend to bog down, but make the moves too slow and the game will also get slower and take longer. You could reduce by 1 MU to keep things moving and reduce LOS so you can't shoot at longer ranges, really would hurt artillery which can only shoot at medium range.

agree with you reduce to 2MU, and 1MU for snow.
Concerning Fog reduce LOS between 3MU to 6MU and after 10 o'clock increase LOS by 3MU until 12MU, then FOG vanish.