Weathervane is a Railroad radiant quest in Fallout 4. It belongs to a chain of semi-random quests provided by Tinker Tom in the Railroad HQ. He thinks the Institute is trying to "terraform" the Commonwealth by poisoning the atmosphere, so he designed atmospheric sensors called MILA to detect any anomalies in the air. He asks the Sole Survivor to help place these devices on high vantage points throughout the city. The number of locations is fixed, but the order in which they are given is random.