The three things I have done to beat the heat are:

1. Get everything off my back. No mess bags or backpacks to prevent airflow. I only ride with panniers and saddlebags now days.

2. Take off my shirt. Might not be as easy for women, but when it is hot and humid out I will go without a shirt or jersey all together. No matter what the jersey makers want me to believe about wicking and cooling properties nothing beats liquid (sweat) evaporating off the skin.

3. Drink water, stay hydrated.