Weird and inconsistent weather FX's

I've made another post about the rain being too white, but this is another issue. First of all, rain and snow effects are inconsistent, there's NEVER snow buildup on the windscreen and sometimes even the rain doesn't build up. Plus, when driving in the rain with the lights on there's this weird lights effect when instead of the road you just light the rain falling, making ths weird 2 dimension effect. As you can see from the 2 images, that's exactly the same stage with the same weather, there's no water on the windscreen (it'll be too white anyway) and in one of the images it seems that it's not raining at all.