How can i get straight hair?

i grew up having wavy hair and as of a few months ago, its starting curling a bit more. my hair is thick and i have a lot of it. i live in florida, and there is a lot of humidity here, so my hair frizzes up a lot. i shower and blow it dry in the morning and straighten it and it looks fine, but in a few hours it frizzes up and the ends start to curl. my hair is a few inches longer than my shoulders and i went to the salon and got long layers so my hair looks less puffy. i don't want to permanently straighten it because it damages the hair. is there any products i can use to help it stay straight and keep the frizz down?