In my experience and conditioning, riding in temps over 100* is like riding in an unrelenting blast furnace and it's tough on the body and mind, even with good fluid intake. I have done it and even after 35 to 50 miles continuous, and sometimes pushing more miles, man... it's hot! Then again, I just posted similar in the 50+ sub forum regarding meds... intense heat with the sunshine that accompanies it... that takes a lot of me.