The shade temperature was 80 (F) when I left for my run and 97 when I returned. Those are *shade* temperatures. Most of my run is in direct sunlight, and the effect of the sun was much worse than the shade temperature would imply.
A couple of times during the run, I started to feel woozy which I recognized as a first sign of heat exhaustion. I drank extra water and Gatorade and felt fine. All together, I drank 20 ounces of water and 20 ounces of Gatorade.
After the first mile warmup, I only took walking breaks at my planned half-mile intervals (well, there were a couple of exceptions to that), but the breaks were usually longer than my normal 30 seconds. My turn-around point was in the tunnel under 126th South, and I stopped for several minutes and enjoyed the shade and breeze blowing through the tunnel.