I don't shy away from the high temps. A bottle just doesn't get me as far as when temps are lower. I take it somewhat easier, but not so easy that I'd be out in those temps longer than needed. Also, if I can average 15 - 16 mph or better for the ride, then the evaporating sweat actually makes it seem a comfortable temp.
My higher fluid consumption does take some planning. Some routes I just can't get water or drink along the way so if I can't take it with me, I just don't go on those routes till cooler days. Shade is also a must, and we have plenty of tall pines, shady oaks and other broad leaf trees. So most roads and trails don't expose you to continuous sun.
It's also somewhat important to remember how quick you heat up when slowing and losing the cooling air flow. At times when climbs or other conditions force me to get below 14 mph the heat starts making itself known again. If I have to get down to 10 mph for very long on a climb, I have to be careful, because I can tell I'm getting into unsafe levels of heat.
Stopping for any length of time is potentially dangerous in or near triple digit heat. Not only do you loose the cooling effect, but the foam liner in a helmet holds heat nicely in the least desirable place for your body to heat up-- the brain! So if I have to stop other than three or four minutes, the helmet is coming off. And since I were sun-sleeves, those get pulled down. They just aren't very effective when stopped or slow on very hot days. I also move to the shade as quick as possible.
Probably if I was in your area, I'd be doing the same as you. It's been a long time since I've been to that part of Texas, but I remember it as being pretty open with shade along roads at a premium.