Does It Rain In The Pantheon?
Actually, it rains pretty frequently in the Pantheon. (For this reason, the floors all slant to the center of the building where there are drains.) And though there are probably going to be more people there when it does rain, just so that they can avoid getting wet themselves, the lack of heat in the building in general and the large diameter of the oculus are really going to lessen any possible updraft effect. Maybe if there happened to be a huge gust of wind that somehow got in the door and pushed its way outward through the oculus, you would get a brief respite, but that floor’s still gonna get wet.