I assume you were joking about a building being so large it has its own microclimate, but I have been inside a building that has its own rain clouds. The building housed a styrofoam factory.

It was always hot and humid in there, probably due to the manufacturing process itself, but not uniformly so. Certain spots would be extra humid, which would cause water vapor to rise up to the ceiling. There were enough particulates in the air for it to then condense into droplets that looked like clouds, which would then create a very light drizzle 20-50 feet away.

I fucking hated that place.