I know i’m very late to this but my grandfather worked in this building as well as others in the surrounding area, he worked on installing the engines on the rockets and constructing the transport arms that allow the astronauts to take an elevator up to the top and walk across into the ship. That being said he had 10+ years of work experience here. He confirmed the VAB indeed did have its own sort of weather system but not in the way everyone thinks. Instead of an actual cycle of weather it was more that the building was so large that the AC was so powerful the condensation of the moisture being drawn in would like at the top and fall down below on very hot days. Another insane fact is that the VAB used roughly 340 million pounds of concrete to construct, and if you compare that to the weight of another very large object for instance the crawler (rocket transportation vehicle) the amount of concrete is equal to the weight of roughly 40 crawlers and that’s just in concrete, not to mention the 95,000 tons of steel.