Weathervane (quest)

The Weathervane Missions are quests in Fallout 4. They are 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.

Quick walkthrough

 * 1) Report to Tinker Tom.
 * 2) Plant MILA device.
 * 3) Report back to Tinker Tom.

Detailed walkthrough
There are eleven quests total in this series:
 * Back Street Apparel
 * Boston Bugle Building
 * Broken monorail
 * Cambridge construction site
 * Camp Kendall
 * Commonwealth Bank
 * Corvega assembly plant
 * Four Leaf fishpacking plant
 * Hub 360
 * Mass Bay Medical Center
 * Parkview Apartments

Back Street Apparel
This location is defended by a group of Raiders and two turrets, one outside on the flatbed truck and the other inside on the ground floor. The Sole Survivor will need to enter the building to gain access to the rooftop where the MILA drop-off location is. Once the MILA has been placed return to Tinker Tom for a reward and a new assignment.

The Boston Bugle
The entrance is through one small door on the side of the building. Take the elevator at the back of the first room you enter. After exiting the elevator you will see a door directly to your right. There is a protectron in the room you exit into. Take this to the roof of the Boston Bugle where you will find the area to place the MILA and return to Tinker Tom for a reward and a new assignment.

Broken Monorail
To reach your location, you must first go inside the Haymarket Mall and fight your way through both Raiders and a few turrets. Keep on climbing up until you reach the roof. Beware, once you exit into the roof, a Deathclaw will be waiting for you. Once the Deathclaw is killed, look around the building until you see a monorail train hanging underneath the highway. In order to enter the train, simply follow the catwalk down. Carefully walk across the monorail train until you reach the end. There you should see a plank where you place your MILA. Once this is done, return to Tinker Tom for a reward and a new assignment.

Camp Kendall
This location is defended by a group of Raiders, some can be found on top of rooftops and will attempt to shoot at the Sole Survivor from range. To gain access to the rooftop the Sole Survivor will need to walk up makeshift ramps towards a button to call a lift that can be used to access the rooftop where the MILA drop-off is. Once the MILA has been placed return to Tinker Tom for a reward and a new assignment.

Commonwealth Bank
The front of the bank is defended by a small group of Raiders and a single turret. Once these are taken care of, the vantage point is accessed by using the elevator by the entrance. When inside the building, taking the elevator next to the one the Sole Survivor exits will lead to the roof of the bank, where one can place the MILA. Once this is done, return to Tinker Tom for a reward and a new assignment.

Four Leaf Fishpacking Plant
The plant is defended by a group of Ghouls, there may also be a pack of Super Mutants in the building to the east if they notice the Sole Survivor. There is an external staircase on the southern corner of the plant for easy access to the rooftop where the MILA can be placed at the northernmost point of the roof. Once the MILA has been placed return to Tinker Tom for a reward and a new assignment.

Hub 360
This location is defended by Super Mutants, to gain access to the rooftop where the MILA drop-off is the Sole Survivor will need to ascend a lift that is located on the Fallen Skybridge, the Fallen Skybridge can be accessed via a staircase south of Goodneighbor. Once inside Hub 360 enter the lift and travel up to the rooftop and place the MILA then return to Tinker Tom for a reward and a new assignment.

Mass Bay Medical Center
The medical center is defended by Gunners and a single Assaultron, there may also be a set of power armor inside the medical center which can be utilized by the Gunners. The Sole Survivor will need to enter the medical center and travel up two elevators to gain access to the rooftop where the MILA drop-off location is. Once the MILA has been placed return to Tinker Tom for a reward and a new assignment.

Parkview Apartments Location
The location is on the top of the building, there are Raiders and Super mutants battling on top of the apartments. Enter the apartments, climb the stairs and the use the elevators to get to the top. Place the MILA on the vantage point and return to Tinker Tom for a reward and a new location.

Cambridge Construction Site
The site is partially walled off and infested by Super Mutants. Head inside and use the staircase to climb the structure while fighting off the mutants, be prepared for an intense fight as there will be a lot of them. At the top of the structure there is a small shack with a red loot chest and a Super Mutant Overlord in it, kill him and place the MILA on the vantage point extending from the shack. (There is also a cooler with good loot perched atop the beams overhead, to reach it carefully inch forward on the outside beam from the shack, climb around the corner and head up the inclined beam upstairs, inch your way over to the cooler on top of the corner beam on the side.) Return to Tinker Tom for a reward and a new location.

Corvega Assembly Plant
The plant is heavily guarded inside and out by Raiders.Head around the back and climb up the structure next to the plant while fighting off raiders. Walk along the sky bridge and onto the plant. Continue fighting off raiders while going up and along the catwalks and at the far end of the catwalk next to the large sphere will be the MILA vantage point (there is also the Repair bobblehead beside the vantage point). Return to Tinker Tom for a reward and a new location.

Bugs

 * If you eliminate The Railroad for the Institute or the Brotherhood of Steel and kill Tinker Tom, you will not fail this quest. It will remain an active quest and direct you to turn it in to Tom's corpse. It is also possible that you will fail one instance of this quest but immediately get another MILA and another quest target to place it (with no possibility to finish).
 * The number of locations can be less then 11 if one or more of locations have alredy been cleaned before. It is not known for sure is it a bug or it was conceived by developers. If one wants to complete all 11 locations despite this, one can use the console command "setstage 000b926a 100" to add the next quest in the chain. (Tested on missing Corvega Assembly Plant quest, needs confirmation for other locations [Worked for Four Leaf Fishpacking Plant - I had never even visited the place])
 * The door - to the Boston Bugle - may not be highlighted, while tracking the mission.