Summer hair question?

I have the kind of hair that, in the humidity, wants to flip out and be wavy when it's straight but but straight when i try to make it curly. so whats a good product to work with my texture in the summertime (it's naturally very straight, the humidity just makes it ...well, very unstraight), and what's a good hairspray to hold a curl? And what's a good product to keep my hair straight? don't say a hair straightener, i will never invest in one since my hair is naturally straight.