Example to reproduce:
one might need to set up a periodic printout to reproduce this behaviour.

Weather weather = GetGame().GetWeather();
Overcast ocast = weather.GetOvercast();
ocast.Set( 0.0, 0, 1 );
Print(ocast.GetActual());

Workaround: using .Set to set the value several times seems to fix the issue, can however introduce yet other bugs.

Generally the weather system is quite quite buggy, hard to read, and very badly designed; it kinda is a shame, that much of it seems hardcoded as well, besides not really working well in sync, but you already know that i think (client not syncing with server weather, which is more predominant on alt+tabbed game)

I already figured out that I have to use this in init.c

Weather weather = g_Game.GetWeather();
weather.MissionWeather(true);    // false = use weather controller from Weather.c

_after_ hive creation, otherwise any changes wont work at all (contrary to the comment in the file)
I have used both, mission weather and normal weather to get this effect.

calling GetWeather before initializing the hive does not allow any changes to weather whatsoever further on, so I might add, that is a prerequisite to reproduce this bug.

I think the main issue is transmitting the value wrong to the client (it should trim below 0 to 0), as it does less havoc on server side. However, it would also be nice if the algorithm actually does what it is supposed to do, and there might be some error in the internal Weather logic.

My current controller script works fine, and just sets the value twice, while lerping the value manually and tries to avoid 0.0 for overcast.