The very best place to start with something that is dealt with the the FAR is to start with the FAR
Start with FAR 1.1. "Special VFR conditions mean meteorological conditions that are less than those required for basic VFR flight in controlled airspace and in which some aircraft are permitted flight under visual flight rules."
The read FAR 91.157.
What does it say to answer your questions? Do you have any questions after reading it? (You probably do)