I rode my bile to work and back today. It was a beauty. The ride in was good. I had a tail wind for at least half the way and it was around 30 degrees.
The ride home was somewhat more challenging. 44 degrees C (111F) when I left work and into a strong headwind, the whole way. It really wasn't too bad. The most interesting aspect of the ride was that my heartrate indicated that I was pushing quite a bit harder than I percieved I was. A ride home with an average heart-rate of 154 would normally be a really hard push. I didn't feel I was pushing that hard, though my legs felt pretty good considering the workout on the weekend.
My heartrate was higher than normal because of the increased need for blood to be circulated near the skin to accelerate the cooling effect of sweating. This has been supported by a number of studies.
To help with cooling, I regularly poored water down the front of my jersey and shorts to accentuate the evaporative cooling effect. Even though this water went on very hot, it quickly cooled down in the breeze. I also drank heaps. I drank only water because I find it very hard to keep a sports drink down when it gets very hot. It's also crap when you poor it over youself.