It's a black widow for sure, but I don't know if it's considered northern or southern, or what the difference between the two. Logic tells me southern because the location is in the south.
body roughly 2 cm
Arachnids are a class (Arachnida) of joint-legged invertebrate animals in the subphylum Chelicerata. All arachnids have eight legs, although the front pair of legs in some species has converted to a sensory function, while in other species, different appendages can grow large enough to take on the appearance of extra pairs of legs. The term is derived from the Greek word ἀράχνη (aráchnē), meaning "spider".