rain

Hello, I'm trying to do a triggered weather system and whenever rain effects are up they just bug out unit formations. If I order a group of units to go somewhere they just completely ignore their formation and end up forming a grotesque and unholy mosh pit. This only happens when it's raining...

One of my custom spells causes a rain, so I use the Weather Effect 'Ashenvale Rain', but it is not visible for the players which particles are set to Low, so they can't see whether the spell is cast.. How do I make every player see the rain?