Kind of ODD! I've had a play around in steam, and re-downloaded version 1.30.16 and tested in-game - back to how it WAS!
Re-set my version to the latest and it remains back to how it was - maybe a phantom setting that we cannot see/change had been adjusted? I think It MIGHT be something to do with my recent truckersmp usage with the winter mod - but i'm not 100% certain it IS! (I'm NOT blaming truckersmp, or their software, merely seeking oppinions on if anyone has encountered similar -we all know how random computers & code can be)
ALL I do know is that I played online on Sunday 17th and it was fine online, but reverting to my single player today I noticed everything regarding rainy weather had increased to 4x the volume as though there was a hurricane blowing outside the cab of my truck!
Ive a vague recollection of noticing something like it before when using another "winter mod" from somebody other than grimes, but alas everthing returned to normal when I disabled the mod.
I will keep you all informed of my progress/findings as I go.