Blast Zone

A blast zone is the resulting irradiated area in Fallout 76 created when a nuclear warhead makes an impact, identified as a red circle on the map.

Background
After completing Mission: Countdown in any of the three nuclear silos, sites Alpha, Bravo, or Charlie, a player character can insert a nuclear keycard and enter the weekly launch codes which grants access to the targeting computer. The player character can then target a location on a military-style version of the map to fire the warhead and trigger Death from Above!.

Before the nuke is launched, a broadcast warning alerts the entire server that a nuclear strike is imminent and an air raid siren sounds. It will take three minutes for the bomb to drop. Upon nuke impact, player characters and most workshop objects inside the blast radius will be destroyed instantly. Anyone inside of an interior cell within the blast radius will be safe from the effects.

Player characters outside the edge of the blast zone will not be killed. Once a player character has entered the zone, they will take severe radiation damage unless wearing power armor, a hazmat suit or Chinese stealth armor. Well-equipped player characters (Level 50+) are recommended for these sites.

These sites are excellent areas to level up and harvest raw flux, which is acquired by harvesting the following mutated flora in nuked zones:

Public events
If a nuke is launched at specific locations on the map, a public event with a high-level boss enemy will begin. The listed location only needs to be contained somewhere within in the entire blast zone radius and does not have to be explicitly targeted as the center of the blast zone.

Protected zone
While where a nuke is launched is dependent on the choice of the player character, certain portions of Appalachia are in a "protected zone" and cannot be targeted. The protected zone includes many areas of Appalachia where low-level player characters are likely to have early quests. If any part of the blast radius would be within the protected zone, the nuke cannot be launched.

Nuclear Winter
In Nuclear Winter, player characters must obtain four launch codes and a nuke briefcase before gaining the ability to drop a nuke. By activating the briefcase, a targeting computer allows the player to drop a nuke anywhere they choose. Similar to Adventure mode, the blast radius will instantly kill any players inside at the time of impact and will leave a red radioactive circle for a duration. Unlike Adventure mode, the countdown timer is reduced to 20 seconds and the blast zone is comparatively smaller.

Bugs

 * If Monongah Mine is within the radius of an active blast zone when another nuke is launched anywhere else on the map, it will trigger another A Colossal Problem event.
 * After playing a round in Nuclear Winter where a nuke was launched, the blast radius may appear many times larger than normal on the map. This is a visual bug only and does not affect the blast zone effects in the world.

Behind the scenes

 * The orange weather seen from inside of a blast zone is a subtle reference to the song "Orange Colored Sky" by Nat King Cole.