Headed out at 07:10am. Target was 06:30, but OH LOOK! SHINY INTERNET! Initial ride was frustrating. It took me until Teasley to realize my chain had popped a rivet. I swapped the chain with my SRAM 951, and all was good. I tried to cut through on Lighthouse, but that would require roaming around someone's sideyard. I looped out and took Robinson to post oak. From there, I took the Denton Katy Trail to Lake Dallas. I stopped at the QT, got another litre of water and a pig-in-a-blanket. I went back out, and rode up the Katy Trail to the Downtown Denton train station. By then, I was already lagging, and the heat was getting to me. A faint headache, low Watts, burning legs from almost any serious exertion, etc. I doubled back to 288 and stopped at the Chevron on I-35 and Lillian Miller for a litre of Gatorade and a Cliff Bar. I checked work email and dilly dallied for 30 mins trying to recouperate from the heat. Not long after I started out again, I realized I'd stopped sweating except the back of my neck. My jersey was dry, as were my arms. My belly was fairly sloshy, but I downed more of the newly cold Gatorade, and in about 15 mins I was back to sweating. I still had no watts, and the last 10 miles were slow. Had to walk up three hills - NorthShore Drive closest to 2499, and two on the trails that parallel Highland Shores RD. Normally I can pedal up those in 2nd or 3rd. I finally made it home about 11:30am, and when i got in the shade, i felt chills like I would begin shivering. I stood under cool water for 15 mins in attempt to be sentient for my 12pm conf call. More than an hour after I got back, and I still have a headache, but am functional. I went through 4 litres of water, involving 2 stops, and 2 snacks. I had a ham sandwich as soon as I got home. I think if I'd hit the road right at 6am, and had my chain situation sorted prior, I would have made it home closer to 9am. The heat and the chain really messed me up.