living here in Central Coast California, my experience is the same. Frost kills in basil . However frost will not harm oregano, in fact my experience is that oregano likes a beating. As to serrano chiles, my suggestion is that you overwinter them. Since they are perrenials (really, they are) they WILL survive frost but not well. cover them with row cover or something to handle the winter months. My habaneros have STILL not produced fruit and my serranos are just setting now, so I will probably do the same :)