Southern exposure line in s1e1

I just started watching this series and I'm wondering, does anyone know the reference behind what Diana says to Matthew when she said, "I'm just surprised you find a southern exposure comfortable"? What did she mean by that line? Is it a vampire thing? I ask because he goes, "You don't believe everything you read, do you?" which made me think she was referencing some kind of trait about vampires that she was clearly mistaken about.