The Ten Year Storm

The Ten year storm occurs once every ten years on the very last day of the year.
The world goes quiet and still. Animals vanish at the premonition of the coming terror. The world sits on edge, holding it's breath. Then the first flakes of snow fall. A gentle lazy dusting of the world and the final chance to take refuge.
By mid day the storm swells. Snow thickens and the winds begin to howl the chorus of death. By nightfall, enough snow has fallen to bar doors. The winds grow stronger, strong enough to blow anything unsecured or unstable. By midnight, the storm's fury is spent and begins to slow, fading back to quiet by sunrise.
These storms will deposit enough snow to bury a full grown man to the hips, sometimes higher. They are highly damaging and bring more casualties than just from the storm's fury and after effects. While the southern countries may be spared the storm's full fury, the floods it can bring are just as brutal. In many countries children born on this date are ritualistically slaughtered. 
Unknown to the rest of the world, the cause of the storm is not supernatural, but magical. What is perceived as the wrath of a god is the renewal of enchantments. The imbalance of magical energies effects the weather patterns, generating the storm. The northern people are aware of it, but prioritize their safety from the barbaric outside world.