You can cause bitter numbing cold with any spell.
Prerequisite: Ability to cast a spell with the cold descriptor
Benefit: You can use this feat to affect any spell that inflicts damage. Upon a failed save the target must make a Fortitude save against the spell’s original Difficulty Class or become slowed for one round, in addition to the normal damage. Spells with this template gain the cold descriptor. If the spell already has the cold descriptor, the Fortitude save is required even upon a successful save. A freezing spell uses up a spell slot of the same level as the spell’s actual level.
Special: This feat cannot be applied to a spell without a saving throw or one with the fire descriptor.