This stuff is amazing. It will not straighten it too well w/o heat. But it actually does fairly well w/o it. I usually let mine air dry (overnight) and then in the morning I straighten it and the results are nothing but FABULOUS! It keeps it straight for the whole day. I don't know how well it holds up in rain, but in humid weathers it's still great. The only thing I could complain about is it's SUPER thick consistency. If overused your hair will feel sticky. Also this isn't Curly Girl approved if you're a curly girl :(