Acid Rain

Acid rain begins to falling within a 40-foot-radius 60-foot-high cylinder centered on a point you choose within range. When a creature moves into the spell's area for the first time in a turn or starts its turn there, the creature must succeed on a Dexterity saving throw or take 8d4 acid damage and becomes covered in acid.

A creature takes 2d4 acid damage if it ends its turn while covered in acid. A creature can clear the acid with an action.

Source: Kibble's Generic Elemental Spells