I grew up there and now when I visit from a colder place I take a maxi dress or two, some capri pants and one pair of long pants. I layer with tanks & shirts, jackets & I take a lightweight scarf. Yes to the flip flops, too. How fancy you are depends on where you go! That’s what I am taking this month when I swing by the check on the old folks.
I just spent six weeks in OC over the winter and everywhere i went in my summer dresses I saw women working in big sweaters, boots, etc., I call it pretending it’s fall 
For me, 60-85, that’s summer.