In WW2OL it turned out to be a disaster. For dynamic weather it takes an awful lot of computing power, let alone writing the code, to generate it. The type of computing power "most" dont have in either AH or WW2OL. So to make it work in WW2OL they wrote the code to generate one single 200" cloud cover over all of Europe at the same time, and for hours, with rain starting and stopping. It wasnt bad for thre ground game but it killed their air game to the point of losing much of their customers before they came to their senses and limited "weather" drastically.
BF4 has decent weather immersion on some maps but whats it matter if most of the rest of the game sucks? And again you need lots of computing power to enjoy it at decent frame rates. I remember some maps with fog in AH that was pretty cool tho I havnt seen them in awhiles. A bit of clouds, fog, and low light would be cool but I think there are other render priorities for AH-lll.