It's a bit too dynamic. Even setting those rain states does not guarantee rain. I've had it stay dry on numerous occasion despite using R04 and R06, rain with clouds presets. Or they generate just a few blobs which can easily miss the track. Only R07 and R08 seem to guarantee rain (torrential rain presets), yet also those can either be a big swath of rain or just a narrow band that flies by. And the dark blue (the torrential part) is sometimes just a line or not present at all.
So it's very random and I guess just like in missions, different when you restart the race. It would be nice to have some more control over the rain. Atm you can't even see at about what time each state will activate. Kinda hard to plan for a nice sunset after the rain when you can't see the time and the game only offers vague presets, afternoon, early dawn, evening, what time is sunrise, how long is day time.
The weather needs to slow down, no idea why it can't generate the weather pattern for the whole race before the start then put it on the radar and animate it at normal speed or according to time acceleration settings. In a 3H race with x8 acceleration (for full day/night) clouds moving at 60 kph in reality would still only move at 480 kph, not 1,500. And 150km look ahead should still take 19 minutes, not 6 which is less than one lap on N24. At 1x speed you would have 2.5 hours visible around you on a 150 km range weather radar.
It's also bugged. Sometimes it rains when it doesn't show any blobs in the center on the radar, sometimes it doesn't rain when it does show blue in the middle. Maybe it's offset as well :/