It was very hot out during the day, but when I was actually riding there was enough wind to keep me pretty comfortable. The problem would be when I stopped riding: my body would still be generating all that heat, with no way for it to cool off. I walked into G&G's all red-faced and sweaty. Fortunately they kindly offered to let me take a shower, which made all of smegs much more enjoyable (for everybody, I'm sure!).
I left for home after midnight, but I have lights and a bright shirt -- the ride home was just fine. Actually aside from being occasionally worried about the dark, it was a very pleasant ride. Cooler temperature and less traffic.