Just like the original rain, this weapon will summon a rain cloud, which will drop acid projectiles straight down on the ground. They burn similarly to flame, causing more damage than rain. If all the drops miraculously hit a tank at distance, it can do 240 damage.
If the player uses acid rain on themselves when they are in the same position as an enemy, the self-damage is actually lower than the damage done to enemies. This is only true for acid rain, as self-damage from acid hail is the same as damage done to enemies.