Did you check out Epic’s “Effects Cave” demo? https://www.unrealengine/blog/new-release-effects-cave-showcase
Not exactly rain, but there’s lots of splashing water, and also snow. 
Did you check out Epic’s “Effects Cave” demo? https://www.unrealengine/blog/new-release-effects-cave-showcase
Not exactly rain, but there’s lots of splashing water, and also snow.