Your hair can still look great even on the steamiest days. Tracy Strycker suggests you cover up your hair when your outside, shampoo it less often , reduce the heat by backing off with hair driers etc, condition regularly and use a detangled comb.
But let's face it: When the air is so thick with humidity it feels like molasses, frizz is going to happen. Don't waste your summer trying to fight frizz. Instead, find an easier low maintenance hair style.