Looks to me like Battlefront 2 uses a post processing for most of the rain, and then has particle emitters near the doors and such.
Those particle emitters near the doors look a bit weird though, you can see it from a distance quite clearly, but maybe that’s just because I’m paying too much attention to it.
The post process and the terrain looks amazing though.
Edit: Watched the video again, I noticed there are some clouds when running outside in the rain. What are those? Seems like either it’s post processing or it’s particle emitters spawning in front of the player/camera. Or they are placed particle emitters that are triggered when walking nearby.