Try to find a shady route to ride. I usually find myself riding home in Va Beach at around 3pm, and it be HOT! Plus I ride a recumbent so I have that mesh seat against my back. I find a lot of riding in the heat (or cold) is mindset. I try to think about all the other athletes who do so much more in much more demanding conditions (Tour de France?). I used to walk to work every day (3 miles) in Newport, RI through the winter. Some mornings it was 5 degrees and windy...sure it was cold, but mindset, mindset, mindset...well, it was still pretty darn cold.
Anyway, shady route?