Your successful Frostbolts, Frostfire Bolts and Frozen Orb hits have a 15% chance, your Blizzard ticks have a 5% chance, and your successful Scorches have a 10% chance to grant you the Fingers of Frost effect.
The Fingers of Frost effect causes your next Ice Lance or Deep Freeze to act as if your target were frozen, and increases Ice Lance damage by 25% for 15 sec.
Ice Lance and Deep Freeze act as if your target were frozen and Ice Lance deals 25% more damage.
Duration: 15 seconds
Fingers of Frost is a passive specialization ability for Frost mages, available at level 24. It gives various spells a chance to grant the Mage a buff that makes their next [Ice Lance] or [Deep Freeze] treat the target as if it were Frozen, as well as increasing Ice Lance damage by 25%.
By treating the target as if it were frozen, Fingers of Frost also benefits from [Shatter].
Instant [Frostfire Bolt] procs from [Brain Freeze] can also benefit from Fingers of Frost, increasing their crit chance.
Being a self-buff and not an actual freeze, this effect works on enemies that are otherwise immune to freezing effects (for instance, raid bosses).
Although [Scorch] is mentioned in Fingers of Frost's tooltip, the spells are exclusively available to different specs - Fire and Frost - and as such it is not possible to use Scorch to trigger Fingers of Frost.
Tips
This talent shines when used in conjunction with [Shatter], causing the spells to be cast under its influence to have a high chance to critically strike. It improves a Frost Mage's mobility by making them able to cast high-damage Ice Lances on the run.
[Frostbolt], 
[Frostfire Bolt], 
[Frozen Orb], 
[Blizzard], 
[Scorch], 
[Ice Lance], 
[Deep Freeze]
[Shatter].
