This spell could be used on normal or magical fires of size up to a 20 ft (6.1 m) cube. The target had to be within 30 ft (9.1 m) of the caster and the spell lasted for two minutes. Higher level casters could extend this range and duration. The hot fire was immediately transformed into blue and white flames that radiated cold and inflicted cold damage on creatures that came into contact with them. The targeted flames had to be relatively permanent—cold fire would work on a small wall of fire but not on the instantaneous burst of a fireball, for example.
If a creature that was vulnerable to cold was the target of cold fire, this spell did cold damage to that creature (instantaneously, like a fireball, but only targeting one creature). Higher level casters could cause more damage. If the creature managed to resist the magic of this spell, it took half the normal damage. If the creature was not especially sensitive to cold, then this spell had no effect.