Well I'm not sure if these can be done but this would be good. The weather could change ingame as your currently playing. Say the weather is cloudy, during the game it can turn to Heavy Raining, stormy weather.
Also, the soldat player will interact with the rainy weather, make it more slippery, harder to shoot because of the rain in the atmosphere. But the weather shouldn't change too constantly if you know what I mean (it will get very annoying to some people). I was just wondering if this could be done and implemented, post your ideas and if you agree.