I recently rode in the blazing heat. I was reminded of how I also rode in some really hot weather last year. You can do so much prep when the mercury starts to climb into the upper 80′s and 90′s, but the main things are staying hydrated, balancing electrolytes, and taking it easy.
On a ride last year, a friend and I went for a 25-mile ride in the heat. It was just under 90 degrees Fahrenheit when we headed out. Although it was warm and humid, proper hydration seemed to help us from dying out there. I drank more water than usual to keep my hydration levels ready for the heat. I also took some CamelBak Elixir to provide additional electrolytes so that I could absorb the fluids better.