Weather

Weather is a feature introduced in Honest Hearts, add-on for Fallout: New Vegas. During the gameplay, the player character can face rain during their travels around Zion.

In the trailer for Fallout 4, it is shown when we get a shot of the Paul Revere Monument, that rain and thunder rages on.

Also, it is also mentioned in Fallout by some Adytum citizens how it will rain soon.