Just like to re-iterate we are trying to move our support to our Q&A section of the website - Simul Support Exchange - Simul
I am checking every now and then but try to focus on the primary channel.
As rain is visible in the RT, as long as the RT is attached you should be good. Make sure you have the translucentRT as a blendable on an unbound post process. I am also aware of an regarding MPU so possibly set to default while you test. Also setting to snow + increasing snowflake size is a great way to test, as you cant miss them. Make sure you are underneath the clouds and the time set is correct in relation to when it should rain. + simulate at least once.
Wind in 4.2a has been removed from keyframes, and it is now a drag and position the keyframes via the Cloud Window. Issues with 4.1a will be fixed but will likely be much slower as it is the depreciated version at point. Quick example of cloud movement for 4.2+ https://www.youtube.com/watch?v=XQ-BDpAR-sY