Weather

Weather is an environmental 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." John Cassidy mentions that the Midwest is a "big ol' radioactive dustbowl now" with "twisters miles wide."

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
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. Radiation storms last for about two in-game hours.

Lorenzo Cabot mentions that the weather cooperated during his trip to Lisbon, but his group experienced a sandstorm in Ubar that caused it to be dark in the mid-morning. The newscaster provides a weather report in the Sole Survivor's pre-War home, reporting that the upcoming weekend would be unseasonably warm with a high temperature of 56. He stated that troops overseas were experiencing unusual weather for autumn as well with cold temperatures at night, continuing to state that a cold front was coming down from Canada, "making it crisp and dry for next week's Halloween festivities." The report ends with a forecast of a high temperature of 52 on the following Monday. The Sole Survivor's spouse will suggest a trip to the park, as the weather is going to hold up.

The weather is mentioned by Paladin Danse, Curie, Drinkin Buddy, Robert MacCready, Porter Gage, and wastelanders. The Gilded grasshopper is a weathervane on top of Faneuil Hall.

Fallout 76
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 and can be seen from a distance as a swirling light-brown dust cloud.

The ATLAS Program, or Atmospheric Terraforming Laser Accelerator System, was a military project on weather modification, successfully creating white-out blizzard conditions in August. The researchers theorized that the system could diminish the threat of nuclear war by sabotaging the enemy via manipulation of the weather. Wavy Willard's Water Park extended their season into October due to mild weather conditions. The owners of Middle Mountain Cabins mention shoveling snow for their guests after a snowstorm. The Pioneer Scouts wrote a guidebook about camping, outlining suggestions for what to pack in case of weather such as high winds and rain.

Post-War weather is mentioned by Ella Ames, including radioactive rainstorms. Rose broadcast the weather on Top of the World Radio, stating that "we're looking at scattered rad storms in the forecast, so cancel those weekend picnic plans!" ATHENA states that "rain does not damage this model of Assaultron. All U.S.S.A. robotics should be suitable for intense space or weather phenomena."