Mythology

Many individual weird things happen on a daily basis but they have at least two converging mythos to them: the events collectively referred to as the Judeo-Christian Apocalypse and the phenomenon known as Silent Jersey. Both are conflicting forces and carry their own strains onto the inhabitants, whether it be physical or psychological.
==The Apocalypse==
The Apocalypse, also known as Armageddon is started when The 66 Seals that bind Lucifer are broken and he is freed.
*The first seal is broken when a righteous Man sheds blood in Hell; Dean ends up breaking the first seal when he spills the blood of a human soul in Hell.
*The last seal by was broken by Sam when he kills Lilith, Lucifer's first Demon.
Many angels including Zachariah and Michael wanted the 66 Seals broken. They believed that this would give Michael the opportunity to kill his younger brother, Lucifer. It is implied by both Castiel and Zachariah that Dean will stop Lucifer. Zachariah later revels that Dean alone cannot possibly stop Lucifer, but he tells Dean that he is Michael's true Vessel.
The four Horsemen seem to play a big part in bringing chaos and destruction to the World. And the Croatoan Virus is a big part of the demonic plan to cause death and chaos on Earth.
*It was up to Pestilence to spread the Croatoan Virus upon humanity. In A&A, a similar event takes place in which a hell Malaria is released into the population. [See Pestilencia]
*It was up to War to manipulate the perception of Humans in order to make humanity fight one another. Status Of Procedure: partial success. [See Iraq War.]
*It was up to Famine to "ride" across the lands with authority and power. Status Of Procedure: failure.
*Lucifer hexed Death by casting a binding spell upon him. Lucifer then attempted to manipulate Death into wiping out 3,000,000 people by sending a "great storm" upon them. Death is stunted in New Jersey thanks to the Fog World.
According to the vision of the future that Zachariah gives Dean, the intended trajectory involves the Croatoan Virus as a key part in the elimination of humanity. Apparently in 2014, all of Heaven bailed and left Earth to be overtaken/ruled by Satan, which would ultimately result in the extermination mankind. In the present the Croatoan virus was released, however this Virus didn't infect the entire World as it did in the 2014 future. Pestilence played an enormous role in eliminating Humanity. This is the future where Hot Lips, Cha-cha and Viper hail from.
==Silent Jersey==
In my restless dreams, I see that town...Silent Hill. -Mary Shepherd-Sunderland [Silent Hill 2]
Silent Jersey is the result of the Fog World infecting the State, just as it originally did with the town of Silent Hill. Unlike the origin town, New Jersey only experiences bouts of Fog, mostly after certain circumstances are met but the end result is the same. Although not as lethal as the hellish Otherworld, it is still a hostile place. Bloodied corpses are not an uncommon sight, nor are wrecked cars. Foggy Jersey is often with many normal doors inexplicably jammed or with broken locks, refusing to allow passage. Also, many doors are locked and the keys to the doors are hidden in bizarre ways as well as doors and passages found in unexpected places such as a soda machine.
The Otherworld is a completely different beast of its own, and it is the closest most of Jersey's inhabitants get to the actual Hell. In fact, a defining characteristic of the Otherworld is the ability to reflect a character's psyche, to twist the environment into their own hell. By consensus, it is depicted as a rusted, ruined dimension. Much of it is composed entirely of rusty brown metal floors and walls, which are often bloodstained as well. Grating, fencing, barbed wires, or entire sections of wall made from flesh and other organic material are also common.