Weather

While all of the Arkham Games take place at night, each game uses different weather effects to create an unique atmosphere.

Clear
There are not any special weather effects in Arkham Asylum, and the sky is mostly clear.

Rain
The opening cutscene has rainfall, and lightning can be heard in the sanitarium. The Batman: Return To Arkham version of the game has constant rainfall in free roam, and rain can be seen on the sunroof glass in the botanical gardens.

Light Snow
The weather in Batman: Arkham City consists of light snow. In addition, small piles of snow can be seen around on rooftops.

Snowfall
Throughout the game, it's constantly snowing, and buildings, roads and vehicles are covered with snow. In the Cold Cold Heart DLC, the sky is now brown/orange.

In addition, a special weather effect, Whiteout, was cut. This weather condition would have lowered the visibility to near zero, forcing Batman to use his Detective vision to see anything. It was removed due to severe performance issues it would cause.

Rain
Rain is the most prominent weather effect. There are three levels of rain: Heavy, Medium and Light.
 * Heavy Rain is present on most Arkham Episodes. In story mode, it appears in the very beginning, and ends after Batman exits Ace Chemicals.
 * Medium Rain falls during the time between Ace Chemicals and Stagg's Airships.
 * Light Rain is present after Stagg's airships and lasts for the remainder of the game, as long as any other weather (below) is not present.

Fear Gas
Around halfway through the game, the city will be covered in fear gas. This limits Batman's movement to the rooftops, and disables every Most Wanted mission besides certain watchtowers. Later, Batman is confined to the Batmobile and cannot leave it until the gas is removed. If Batman manages to finish a Most Wanted milestone and calls Alfred - such as clearing all the aerial drones - Alfred will sarcastically remark about his reluctance to clear the gas.

Pollen
This weather effect is automatically present after the fear gas dissipates. There will be pollen flying around, and the ground and rooftops are covered with green substance. The effect ends if the player enters the militia HQ or waits long enough.

Snowfall
Appears after the In From the Cold Most Wanted mission is completed. It will make way for any other special weather effects. If the story mode is complete, the effect's duration is unknown, but some sources say it's permanent. The ground will also be covered with snow. (The ground snow appears to be recoloured pollen)

Snow also appears on the DLC map Psychiatricks.

Clear
Clear is one of the weathers that are not normally accessible, and appears only in pre-rendered cutscenes. After the full Knightfall protocol is activated, the weather will be clear during James Gordon's speech.

Glitches

 * At places, the constant snowfall in Batman: Arkham Origins can lower the framerate.
 * According to the developers, Heavy Rain appearing in the beginning of Knight's story was a glitch. They however agreed to re-add the effect, as both players and the team that created the weather effects preferred the heavy rain. It was restored in December for PC users, and in January for Console users.
 * Several rain effects on Alternate Batsuits had glitched rain effects before the December update. For example, the plate covering the nape in Origins suit had no rain effects whatsoever, and several suits had the rain "fall" upwards.