|“|| I hear that it's almost never sunny in Silent Hill. And people say that when the fog comes out, strange things happen.
The Fog World or Misty World (shown in the tips menu of Silent Hill: Origins) is the name given to the dimension that lies alongside the "Real World" and the hellish Otherworld of Silent Hill. The Fog World can also simply be seen as another side of the Otherworld, though the exact definition is unclear. It has been compared to NREM (non-rapid eye movement) sleep, which is the period before heavy dreaming. 
The process by which an individual passes into the Fog World from the Real World is not often touched upon in-game, but each time it occurs, it is typically depicted as a gradual transition, with most characters not even realizing that something is amiss until their first encounter with one of the town's creatures.
In the games, the Fog World appears to be an almost exact copy of its Real World counterpart, except that it is perpetually shrouded in a thick fog and seems almost completely uninhabited. The fog usually tends to be white or light-greyish in color. In Silent Hill: Homecoming and Silent Hill: Downpour, however, the fog has a much darker tinge that is reminiscent of smoke.
While the Fog World is considerably less macabre than the Otherworld, it is still a relatively hostile environment, in part due to the monsters that roam freely. The various locales in the Fog World appear to be in a constant state of disrepair and almost completely deserted, with the exception of the town's monsters and a handful of individuals. Bloodied corpses and wrecked cars are fairly common sights in this dimension. Its roads often drop off into deep abysses, which prevent any means of escape for its inhabitants.
In the original game, snow appears to fall in this world, while in the film and Silent Hill: Homecoming, ashes fall from the sky instead. Silent Hill: Shattered Memories reintroduces the element of snowfall and in Silent Hill: Downpour, heavy rain becomes a common occurrence. In the other installments, the Fog World lacks any of the additional effects listed.
The Fog World is often constructed like a labyrinth, with many normal doors inexplicably jammed or with broken locks, that prevent passage. Also, many doors are locked with their keys hidden in bizarre places; for example, a key can be found inside of a soda can from a vending machine in Silent Hill 3. The Fog World can also expand into nearby towns, such as Shepherd's Glen in Homecoming, in order to punish certain people involved with the history of Silent Hill.
Many suggest that the Fog World was created in the first game for the purpose of hiding the game's graphical limitations. However, many fans and critics have praised the fog, stating that it created a "spooky" or "gloomy" environment.
Another popular idea is that Alessa Gillespie created the fog to give the world a limited view to visitors, since she herself never saw much of the world around her, and as such, left an imprint which causes the Fog World to appear to other people. The fog could also be a memory of the smoke from the fire Alessa was burnt in at the beginning of Silent Hill: Origins, as Travis Grady says "not fog... it's smoke" when he sees her burning house. This theory intersects the fact that the siren sound heard before the shift to the Otherworld is a print of the medical vehicles sirens that are heard after the burning of the Gillespie house. It could also explain the ashes falling from the sky in the film and in Silent Hill: Homecoming.
It is also speculated that the reason the later protagonists are exposed to fog is that it is the fog of the mind/memory. This seems the most likely in James Sunderland's case, as he last visited Silent Hill some time before the events of the second game. This theory is supported by the fact that when the Fog World transitions to the Otherworld, everything becomes much clearer, if not more terrifying, which could serve as a metaphor for the character clearing the fog from his or her mind, and facing/owning up to the terrible truths of their past.
In the film, it is implied that the Fog World was created by Alessa Gillespie and Dark Alessa at the same time as the Otherworld to entrap the cultists. The Otherworld's symbolism of Alessa after she was burned, as well as the symbolism of the change between the two realities representing what was done to Alessa's body, suggests that the Fog World is a representation of who Alessa was before she was burned alive. This would explain the almost total lack of monsters in the film's version of the Fog World, as well as the feeling of abandonment and isolation. According to director Christophe Gans, the ashes in the film's version of the Fog World represent the fires burning in the Otherworld.
Silent Hill 2
Silent Hill 3
Silent Hill: Origins
Silent Hill: Homecoming
Silent Hill: Downpour
Silent Hill film
|Rose Da Silva - Christopher Da Silva - Cybil Bennett - Dahlia Gillespie - Thomas Gucci - Anna - Christabella - Sharon Da Silva - Alessa Gillespie - Dark Alessa|
|Sister Margaret - Eleanor - Colin - Lisa Garland - Order Soldier - Jennifer Carroll|
|Pyramid Head - Creeper - Armless Man - Colin - Nurse - Grey Child|
|Bowling Alley - Brahms - Brookhaven Hospital - Church - Da Silva House - Gans County - Grand Hotel - Midwich Elementary School - Nathan Drugs - Sacrificial Chamber - Silent Hill, West Virginia - Toluca County Archives - Toluca County Mining Museum - Toluca County Orphanage - Toluca Lake - Smitty's|
|The Brethren - Monster - Flashlight - Manifestation - Otherworld - Fog World - Real World - Siren - Great Knife - Welcome Sign - Brethren Symbol|
|Heather Mason - Christopher Da Silva - Vincent Cooper - Claudia Wolf - Leonard Wolf - Dark Alessa - Douglas Cartland - Alessa Gillespie|
|Rose Da Silva - Dahlia Gillespie - Suki - Travis Grady - Order Soldier - Detective Santini - Mannequin Girl|
|Armless Man - Delusion - Leonard Wolf - Lobotomy - Mannequin Monster - Memory of Alessa - Missionary - Nurse - Pyramid Head - Valtiel|
|All Hallows High School - Brookhaven Asylum - Central Square Shopping Center - Jacks Inn - Sanctuary - Silent Hill, West Virginia - Lakeside Amusement Park|
|The Brethren - Halo of the Sun - Monster - Manifestation - Otherworld - Fog World - Real World - Robbie the Rabbit - Seal of Metatron - Siren - The Order - Great Knife - Welcome Sign|