How in the hell do you stay comfortable at that temp? I know you guys don't have to deal with the humidity like we do up here, but that is still damn hot.
Uh... You must be thinking about Arid-zona.
Source:
http://ggweather.com/ccd/avgrh.htm
Dallas Fort Worth average relative humidity (first number is morning, second number is afternoon) -
June: 85 58
July: 79 52
August: 79 52
Detroit Michigan average relative humidity -
June: 79 54
July: 82 54
August: 86 56
Not a hell of a lot of difference there. Gets worse the further south you go; Houston is called Humidston for a reason. Sweating doesn't do you a lot of good there, the air is too saturated for it to evaporate quickly.
Houston -
June: 92 64
July: 92 62
August: 92 62
Just for comparison:
Phoenix -
June: 30 12
July: 43 20
August: 50 24
Getting stranded in the middle of the Sahara is more comfortable than Dallas in high summer heat.
As for the other part of your question, there are multiple strategies riders use. Among them are active cooling vests, mesh gear, perforated gear, evaporative (or other tech) cooling collars (which are surprisingly effective), soaking the clothes one wears under ventilated gear in water prior to riding, and others. Evaporative cooling concepts don't work unless you generate a fairly high wind around here due to the high relative humidity, so we speed a lot more than usual so our body cooling systems work (if that's the tech we're using.) Hydration on runs is of paramount importance and being alert for signs of imminent heat stroke is something you just do - and you treat for that right the hell now the second you see the first symptoms.
Basically, the bottom line for us is 'keep moving' like certain kinds of sharks.