In central Louisiana in July, we had many days with heat indices>100. Sweat would not evaporate to cool my body, but all my body knows to keep cool is to sweat. I lose copious quantities of water and electrolytes in said conditions. I resorted to a Camelbak full of ice to try to stay cool. Early August, and heat indices have moderated at least a little. Still, bike clothes are wringing wet after most rides, including shoes. My shoes are so wet that I'll leave my shoes outside to dry in the sun after rides.