Rain is something more \"client sided\" rather than server side, so I think they were just playing with it, as it has happened in the past.
It is true that rain is quite rare in PS, but it is also true that for a certain period some installer didn\'t have the CS plugins for rain and snow (I think it was the MacOS one).
Anyway, the feature has been not so much used because of the bugs, crashes, and whatever it was generating.
I have been working on these issues during the latest months, and I am quite confident that things are getting better. I have fixed some things and I have tested them, but a more massive kind of test is surely needed.
THis will happen for sure, when the next client will be released.
And this will happen when things will get better with the amount of bugs we have had lately, and with the stability of the server.