Weather

Weather is a feature introduced in the Fallout: New Vegas add-on Honest Hearts. Additional weather patterns were developed for Fallout 4 and Fallout 76.

Fallout
The Adytum citizens comment on the likelihood of rain soon, others note how previous rainfalls have been "glowing."

Fallout 2
The California area is suffering through a drought, following an unusually short rainy season. A random encounter with a weary fisherman reveals there is apparently a regular "season of storms."

Fallout 3
In Anchorage, the entire environment is covered in snow. Sergeant Benjamin Montgomery asks the Lone Wanderer "and I'm supposed to kill the Chinese with what? Snowballs?" if they ask for too much ammunition. General Chase mentions that there is blood outside on the snow. At Chinese Forward Camp Delta, there are three snowmen wearing various pieces of armor, clothing, and one holds a downscaled U.S. flag.

In one of the Tranquility lounger simulations, Stanislaus Braun mentions that during the Slalom Chalet simulation, Old Lady Dithers slipped on ice and impaled herself on a wrought-iron fence. He added that he thought there was nothing "more sublime than that bold crimson on fresh-fallen snow."

Fallout: New Vegas
Fallout: New Vegas was the first game in the series to introduce weather. The player character will experience frequent rainstorms during their travels around Zion Canyon. A Weather Monitoring Station is located on top of Fortification Hill in the Mojave.

Randall Clark wrote about the weather that occurred immediately after the Great War while he sheltered in Zion. A week after the bombs, he mentions black rain was falling. The following January, he comments on a windstorm that reduced radiation levels and snow that glows green.

Snow covers the Mount Charleston and Jacobstown area. Cass comments on the snow if she is brought along to Jacobstown, stating that the place is cold and she wishes she would have brought a jacket. She comments that she has "only seen snow, not walked through it" and states "Crazy - frozen water? Should package this shit." Super mutants around the Jacobstown Lodge comment that they hope it will snow later.

Fallout 4
Fallout 4, compared to the previous games has a much more immersive real-time weather system. The world alternates between clear skies, assorted degrees of overcast, fog, and rain. The length of these varies and progresses naturally as the day goes on. There is a chance for thunder while it is raining at night.

On occasion, a radstorm may occur. During this time, the outside world will gain a green tinge, and occasional flashes of lightning will inflict radiation damage to the Sole Survivor. Although lightning strikes, it doesn't rain during radiation storms. Radiation storms last for about two in-game hours. Weather can be changed using weather ID console commands.

Fallout 76
Fallout 76 built upon and expanded the real-time weather system from Fallout 4. In addition to overcast, fog, and rain, the game introduced ash storms and radioactive, post-nuclear dust clouds. Rain clouds and radstorms in Fallout 76 move across the map and can be seen from a distance. Each region of Appalachia has different chances of weather types occurring.

Ash storms occur within the Ash Heap, primarily near Mount Blair. A heavy gray haze blankets the area, lowering visibility. This effect is amplified when facing toward the sun and looking outside from the interiors.

Post-nuke dust clouds are localized within blast zones, the player character-designated areas targeted by a nuclear missile. The area is enclosed in a yellow-orange haze with occasional flashes of lighting. The contaminated environment inflicts severe radiation damage without the proper protection, causing death. The area can be seen from a distance as a swirling light-brown dust cloud.