Interesting article in today's Dallas Morning News on cycling in 100 degree + weather. Popsicle Ride, BikeMart Wednesday night ride, and HHH ride were mentioned in the article. RBENT member, Daniel Schaaf (square-corners), was interviewed for the article. Excerpts: "And medical experts say that a fit, heat-acclimated rider who drinks enough water and pays attention to symptoms of potential heat injury is probably profiting from the exertion." "I believe they are getting exercise benefits, said Craig Crandall, a cardiology professor at UT Southwestern Medical Center..."

Quote from shellbear on Aug 9^th, 2011, 9:01pm:

quoting Clint Eastwood,eah I'm with you,I go out near sunrise to play on the streets, plus the Hulen Mall parking lot is like a roller coaster world with bonus play time on the elevated ramps. Also the sprinkler systems there are on that time of day and you can ride in them to cool down   I rode 7 miles in the playland and adjoining roads including South today.

Heat adds another stress, and stressing your body makes it stronger. I've noticed that I run a higher heart rate compared to my perceived effort on extremely hot days.  
 
Lots of us like to test our limits. But testing your limits with extreme heat involved can be dangerous, hence all the warnings we hear. I've pedaled home all these 105+ degree afternoons, on a faired bike, even. I haven't felt close to being in trouble this summer, but some of the heat related problems can sneak up on you without much warning, so I try not to get carried away with my effort on the really hot days.
 
Some of us are able to acclimate better to heat than others, too. So, it's one of those things where you have to watch out for yourself.

I'm also from the Northeast...really.  From Massachusetts.  When I got here, in 2000, I only rode at night during the summer.  Then, I got tired of not working out during the day, so I rode bit by bit during the day, increasing slowly, and resting when the machine needed it.  I've been doing that all these years, and now I can go all day.  When we're looking at 107 or so degrees, I do make liberal use of the shade, again when the body calls for it.  Not only do I carry a gallon of water in my trailer during these rides, but I really focus on nutrition the day before, and I eat (not much) at some point during the ride when they are over 30 miles in the heat.

Based on the comment string above, my weekend writeup seems to fit right in as a reply.
I had planned on the Mineral Wells 400k this past weekend, but at the last second, switched to the 600k. I wanted to ride both days but knew it was unlikely I would ride Sunday after doing a 400k on Saturday, especially in this kind of heat.
Unlike last September, when I last did this ride, this was not a perfect weekend for a long ride. HEAT was the big issue. We didn't have that much bad chip seal and the wind wasn't very strong, but when it got hot, whatever wind we had, felt like someone had left the hair dryer on, right in our faces!
I used my cooling vest more efficiently this entire weekend, thanks to pre-ride advice on that subject. I followed the "best practice" suggested and enjoyed many more hours of cooling than previous attempts had netted. As a result, I probably had the least trouble with the heat this weekend. But, we took long breaks wherever we could, topping off bottles and camelbaks with ice, at every opportunity. I never would have attempted a ride this long in this kind of summer heat without the aid of the cooling vest and electrolyte replacement I've come to depend on. I doubt that the absence of one or the other would have been good enough as we experienced sun temperature up to 116° on Saturday and shade temp of 108°. It was a little cooler on Sunday, with temp topping out at 107° in the shade. No reason to go into details of the ride - we did ride straight thru, only to take advantage of all night cooler temps. That did not help us avoid full daylight heat on day 2 - just meant we didn't have to do as many miles in the full heat! Total miles was 374 and climbing of just over 12000 ft. The average was pretty slow, at 15.2 for the entire ride, but given the conditions, not really that bad!