No, it's very noticeable. Instead of being hot and damp you've got cold that chills you to the bone and you're still really sticky and damp. It doesn't hurt that things stay very foggy so you can pretty much see the humidity (but not the silver painted trams).
Yes, there are a lot of microclimates here and I suppose in some mold could be likely.
To that point though, most of the neighborhoods I have lived in have had little to no fog. Russian Hill being the exception. I’m not sure how much of a difference that makes in indoor relative humidity or chance of mold.