Apologies for the issue guys. Seems like there must be a bug somewhere - I'm not sure where the rain is coming from!
The scripted weather is set to "clear", and the weather plugin is not running (I did start it at one point yesterday, but there does not appear to be a persisted, rogue process still running... not to mention that the current weather at Imola is actually 8 and sunny).
Something somewhere has gone seriously wrong. I shall restart the server now. Apologies for the inconvenience.
If somebody could please confirm whether or not the rain has stopped, after the restart, that would be great.
EDIT: server has been restarted. Hopefully this won't happen again. I think it had something to do with me opening the weather server application yesterday, and subsequently closing it without restarting the server again afterwards, which in turn messed up the weather. It was also clear at Imola yesterday, but as soon as the rFactor 2 weather system gets into a muddle it just rains, constantly. Sorry again folks.