When a fire storm spell is cast, the whole area is shot through with sheets of roaring flame. The raging flames do not harm natural vegetation, ground cover, or any plant creatures in the area that you wish to exclude from damage. Any other creature within the area takes 1d6 points of fire damage per caster level (maximum 20d6). Creatures that fail their Reflex save catch on fire, taking 4d6 points of fire damage each round until the flames are extinguished. Extinguishing the flames is a full-round action that requires a DC 20 Reflex save.