Weather in Custom Battles Out of Control

While I am in the process of setting up a custom battle I see a blank space in the weather slot so I don't get to choose the weather type for that battle. One recent battle was fought in the fog in which enemy archers hid as they somehow managed to shoot at my army. I had trouble finding them and even my own troops at times. My other recent custom battle was fought during a lightning storm and that was pretty much the same deal with even worse weather. Is there a fix for this? I could sure use one.

It depends on the map you chose. On some maps, usually the ones for the historical battles, there is no option to chose the weather by purpose. Real generals couldn't influence the weather either. Try a map further down the list.

I believe the maps that you CANNOT build settlements on (they are first on the list and have a gray icon next to them) have random weather. On the other 'regular' maps you can choose the weather. If you don't like the weather just start the battle over again from the main screen and choose "load previous custom battle". If you end the battle and chose "replay this battle" from the defeat screen you get the same weather in my experience.

There is a descr_battle file for each of the nonmodifiable custom maps that dictate weather.
However, those don't seem to work I believe, as grassy plains can sometimes give you lightning storms even though it is listed as clear.

I had a second look at the historical battles but those list the same and work in contrast to the normal custom maps oddly enough. Maybe something in the wfc file.