Not sure if this has been reported already - I've had look on the forums but couldn't find anything similar. So I started racing with the 1960's cars in Monaco today and really enjoyed it, so I decided to play with the settings a bit and at 50% I added some rain. When I got to 50% in the race I could hear the rain on the main straight but couldn't actually see it. When I got to about a 1/4 of a lap the rain appeared, but when I drove through the tunnel I could still see the rain (inside of the tunnel). After I drove out of the tunnel, the rain suddenly disappeared and appeared again 1/4 into the next lap. This happened on every lap I drove so far (I have not tried the track with any other cars though).