Blizz is a biochemical weapon that appeared and played an important role in the Master of Horror's episode, Dance of the Dead.
In 2008, a group of unspecified terrorists were able to develop a chemical weapon. The creation of this weapon led to World War III, and soon Blizz was used to create large massacres in the US. Once released in the atmosphere, Blizz alters the local weather patterns, from clouds and rain down as black, ash-like flakes. Burning people's skin on contact, it was a very destructive weapon. Several states, like California and New York became devoid of life and uninhabitable after severe Blizz attacks.
One notable use of Blizz was on the 7th Birthday of Peggy. Halfway her birthday party, Blizz was released in the atmosphere and rain down on the garden. Her mother Kate dragged her and her sister Anna to their house, before locking the door. Her mother would refuse to let any of the others inside and they watched in horror as her friends and their parents died from exposure to Blizz.
Blizz is very potent chemical weapon which changed weather patterns, making it almost unescapable and allow it to be spread over large surfaces, making thousand if not million victims at a time. A single Blizz-flake caused severe burns to its victim and burned through clothing, leaving the victims permanently disfigured. Prolonged or heavy exposure to Blizz would result in the death of said person. Based on the reaction of Kate, it is possible that also has a contagious side to it, as she refused to offer any help to the other victims.