After testing it appears everything is working now, so I am re-releasing a 3rd party mod as "client fixed".
Meaning:
All effects clientside, no more replication of single drops over the network.
Added features (rain-puddles can be turned off)
Bug fixes (zone change did not register...)
Krull added snowflakes too so you can use it for snow as well
http://ws.online.de/projects/Unreal/fil ... C225cl.zip
Happy mapping