About fog... I would like to appeal to people who are really deep into environmental modding. Amount of foggy days/nights in this game is ridiculous and have nothing to do with reality. In real world fog is very rare in open ocean or sea and happens when air above the water surface is suddenly cools down a lot (like sudden move of cold front in atmosphere). Not to mention it usually happens in early morning hours and does not last past noon.
Sorry but it got under my skin especially when I had to sink billions of tons of specific ships in North Atlantic in winter 1940/41 and my most common weather reports were: " Clouds overcast, participation heavy, fog heavy, wind 15m/sec". And I had to find tankers in conditions like this. I don't mind if it last couple of days. But it lasted like 3 months and this is a total crap. I know what stormy weather is, North Atlantic and North Sea are pretty rough at early spring and late fall but not foggy. It takes warm water and cold air for that. I would like to take people who come up with the idea of fog amount in this game to somewhere where convoy routes are, drop them into the water in late October and let them speak about how warm water is and how cold is air. And then I would tell them that they are allowed back on ship only after fog will show up.

I am more than sure they will not make it back home.
Anyway.. If time space in game equally divided as follows:
25% no fog
25% light fog
25% medium fog
25% heavy fog
Guess what? We spend 75% with some kind of fog. And this is as far from reality as possible. I've spend some time at sea. I've seen fog only in early morning hours in English Channel and off the coast of Corsica/ Sardinia in Mediterranian. And it never lasted more than 4-6 hours. No way it lasted days after days like in this game.
I would say for reality sake it should be redistributed (if it is possible) following way:
40% - absolutely clear (no fog).
30% - little haze, that happens often enough to consider (light fog).
20% - medium fog.
10% - heavy fog.
Region does not matter much.
Another thing - in reality it is raining more often than in the game

.
But let's fix that fog thing first, please.