My advice might not do you any good, because I don't have this problem...
What I can tell you is that the best thing to do would probably be to use an anti-humidity hair product. Whether it be a leave-in serum, something to use while blow drying your hair, or even some hairspray, those kinds of products are desgined to keep your hair looking as anti-frizzy as possible.
Hair that's dry and has crispy ends tends to get poofy in humidity. Do you dye your hair? Because that tends to dry it out and kill it. :P Most hair products (like hair spray and gel) dry out your hair because of all the chemicals in it, too.
Continue using conditioner, and if you do dye your hair, perhaps it would be best to stop, let the colour grow out and see how it affects your hair. I used to dye mine but it's been my natural colour for a few years now and I've noticed a huge difference.
Also, when I let my hair curl naturally, I use this stuff called Biosilk Silk Therapy. It's in the form of a serum. It works wonders with the frizz, and it's gentle on my hair, too. Maybe it'll work for you, too.