All I can think of is The Californians, that SNL skit about blonde valley-girl types. They mentioned a "September" character, so I guess that goes to show what people think of when they hear that "name".
I think it's the "-ember" part that gives it that bit of airheadedness. It's a pretty word though, I love the "Sept-" beginning. I don't mind it, I'd be happy to know a September.