This morning on my way to what I call “work,” the answer came to me.
It appears clouds emanate from 475 Brannan Street. I pointed out the stream of clouds coming through a pipe on the roof to several other pedestrians, and they seemed to agree that the billowing clouds behind the building – and nowhere else in the sky – came from this very localized place.
While these photos were from a couple of days ago at Union Square (and you must admit these ARE killer pics of clouds and light rarely seen in the city), I do maintain that at least part of San Francisco can attribute its cloud cover to this one building.
So there you have it, an answer to your kids’ question, no thanks to Wikipedia.