Virtual Weather is an umbrella term for meteorological phenomenon on Lyoko, Replikas, other virtual worlds like the Cortex (Replika) and the Volcano Replika, and in the Digital Sea. This article lists the various observed kinds.
X.A.N.A. showed the ability to create sandstorms in "Log Book", in the form of a large tornado. This decreased visibility significantly. X.A.N.A. used it to hide a Megatank. This has only been observed in the Desert Sector.
Mountain Fog is exactly what it sounds like. It is fog in the Mountain Sector. This is always present in the Mountain Sector to a degree. However, sometimes it gets a lot thicker. This thickening was observed in "Tip-Top Shape" and "Revelation". In "Revelation", it was used to hide the approach of 3 Tarantulas. In "Tip-Top Shape", X.A.N.A. fogged over the entire sector to make it harder to navigate.
Digital Sea Flooding
In "Tidal Wave", the Digital Sea overflowed, and flooded the surface remaining surface Sectors with the digital sea. This was also caused by X.A.N.A.., and had to be repaired in Carthage. This did not affect the Towers or the sectors, but was lethal to Monsters and Avatars.
In most appearances of the Cortex, a lot of clouds are visible beyond the land of the sector. The clouds surround the area, but don't touch it directly. Instead, there appears to be a buffer zone of neither land nor clouds, which is about half as wide as the land covered part of the Cortex itself. This also appears in the concept art.
Glacial Expansion and Contraction
Rather than being a natural phenomenon, the growth and shrinking of ice in the Ice Sector appears to be entirely artificial. In "Down to Earth", Jeremie's Multi Agent System was used to radically expand the ice in the sector, to constrain the Kolossus. In several episodes, such as "Saint Valentine's Day" and "Vertigo", Aelita used her Creativity to expand the ice to constrain or block enemies.
Glacial Breakup and Drift
Like Glacial Expansion and Contraction, Glacial Breakup and Drifting is mostly artificial. In "Temptation", Tarantulas fired repetitive shots at the ground, causing it to fracture and break up. Rather than being a discrete landmass, the area became a bunch of small glaciers. Due to everyone moving on them, as well as the normal water physics in the Ice Sector, the glaciers shifted around a lot.
Digital Sea Waves
Despite looking peaceful at a distance, the surface of the Digital sea is actually very turbulent. The waves are obvious in any shot close to the surface. In Code Lyoko Evolution, this effect was toned down a little.
Like the digital sea, the lava in the Volcano Sector has a turbulent surface layer, when observed closely. This is actually rendered using the same effects and animation object recolored. This phenomenon was only observed in Code Lyoko: Fall of X.A.N.A. and Code Lyoko: Quest for Infinity.
Virtual Water is the presence of ponds on Lyoko. Unlike the Digital Sea, this is completely harmless and mostly decorative. It can be seen in the Ice Sector and the Forest Sector. In the Forest, it was seen in "Temptation", Code Lyoko: Quest for Infinity, and "Opening Act". In the Ice Sector, it's extremely common. In "Vertigo", Odd swam in it.
Earthquakes are one of the more common phenomenon in both the virtual and real world. In "Just in Time", X.A.N.A. caused a chain of earthquakes in Boulogne-Billancourt. X.A.N.A. also caused several earthquakes mentioned but not shown in "Code Lyoko: Quest for Infinity" and "Code Lyoko: Fall of X.A.N.A.". The most common example of earthquakes is in the Cortex (Replika). There, earthquakes typically precede the Cortex Shifts.
Cortex and Carthage Shifts
Cortex Shifts and Carthage Shifts are two closely related phenomenon. In Carthage, the Carthage Replika, and The Cortex (Replika); the massive blocks that the sector is made out of can shift around. In the case of the Cortex, this is a security feature/ byproduct of incomplete code. In the Carthage Replika, this was a security feature left in place by X.A.N.A., after he copied the code for the original Carthage.
In Carthage's case, this phenomenon is highly diverse. It occurs in the key chamber whenever one hits a Key Mechanism, allowing them to climb. It also occurs whenever the Carthage Security Countdown hits zero, potentially trapping or Devirtualizing the victim. Other instances include whenever the Transport Orb arrives in the Core Zone, as the sector rearanges. Some block shifting is also present in the form of a trap. Variations of this include collapsing floors, shifting floors, people being crushed, etc. In the video games, Carthage shifting is a major obstacle. Finally, whenever somebody hits the key mechanism before the countdown hits zero, some blocks shift to reveal the Elevator.
This phenomenon is extremely dangerous. In "Cortex (episode)" and "Exploration", several people were devirtualized by being crushed, and weren't easily rematerializeable. This was rectified by configuring the sectors to work with the Materialization Program. People also can get trapped, which happened to Aelita Schaeffer.
A point of confusion is the incident in "Plagued", when a massive platform in the Desert Sector rotated to a 90 degree angle. This wasn't a natural phenomenon. This was X.A.N.A. using the Sector Alteration Program.
Sector Collapse and Deletion
Sector Collapse And Deletion is a rare phenomenon that occurs to Sectors or Replikas when the hardware that supports them is damaged, or the software supporting them is halted or fails. In non-Cortex areas, the phenomenon, as observed in the sector, consists of the colored panels of the sector dissolving away in patches, with the vector lines receding afterwards, in patches. This includes the dissolution of Lyoko Wires and Towers. In the Cortex, this consists of the various modules of the Cortex falling into the Digital Sea in pieces, in a pattern emanating outward from the center. In worlds where the sector in question is the only sector, such as Replikas, the Virtual World Shell usually explodes afterwards.
- "Common Interest": This was a partial example. It occurred in the Ice Sector, and caused by a dying battery in the Supercomputer.
- "Lyoko Minus One": This was the first complete example. It occurred in the Forest Sector. The cause was the use of X.A.N.A. (code) in the Way Tower.
- "Sabotage": It occurred in the Ice Sector. The cause was the use of X.A.N.A. (code).
- "The Pretender": It occurred in the Desert Sector. The cause was the use of X.A.N.A. (code).
- "Double Trouble": It occurred in the Mountain Sector. The cause was the use of X.A.N.A. (code).
- "Bragging Rights": Forest Replika, Supercomputer Sabotage.
- "Hard Luck": Forest Replika, Supercomputer Sabotage.
- "Bragging Rights": Forest Replika, Supercomputer Sabotage.
- "Hard Luck": Desert Replika, Supercomputer Sabotage.
- "A Space Oddity": Carthage Replika, Supercomputer Sabotage.
- "Fight to the Finish": Ice Replika, plus a bunch of others, Jeremie Belpois's Multi Agent Program.
- "Ultimate Mission": Cortex, a virus.
- "Code Lyoko: Quest for Infinity": Desert Replika, Forest Replika, Ice Replika, Mountain Replika, and the Volcano Replika, multiple causes, including supercomputer sabotage and Code: Chimera.
- "Code Lyoko: Fall of X.A.N.A.": Desert Replika, Forest Replika, Ice Replika, and Mountain Replika; supercomputer sabotage.