Texan here too. I start on heat adaptation early in the year, exercising at midday whenever possible. Usually by July I'm heat adapted well enough to bicycle at easy to moderate effort but this year has been brutal. In previous years riding in midday heat was no problem, but I turned 65 a few months ago and it's catching up with me now.
So I've switched to brisk walking for 3-7 miles a few days a week, mid afternoon at the hottest. It's easier to regulate my perceived effort. With bicycling hills are always a struggle even in the easiest gear, and there's no coasting uphill. I'll do a little brief jogging during the walks, usually for 30-60 seconds at a time, but never force my body beyond the comfort zone. That heat penalty adds up quickly.
For walking and jogging I always wear a hydration backpack or carry a liter thermos of ice water with electrolytes. For cycling I always carry at least two bottles, one with electrolytes, the other plain water -- and sometimes wear the hydration backpack as well. My go-to electrolyte mix is DripDrop. There are others but DripDrop works best for me. Nothing magical, no secret ingredients, just the formula adopted by the WHO for a standard oral rehydration solution, including a small amount of plain sugar which helps with rapid absorption in the stomach and gut. Plain water and artificial sweeteners tend to make me feel bloated when I'm drinking a lot of water to stay ahead of dehydration.
I've been riding late at night, sometimes after midnight. Cooler, less traffic, I only need to watch for critters and debris. I use two bright headlights, one of which is NiteRider's brightest, a Lumina Dual 1800 with a shaped cutoff beam like a motorcycle or motor vehicle lamp -- wide enough to cover shoulder to shoulder on a two lane blacktop, but doesn't spill over into the eyes of oncoming traffic. Pricey but worth it.
My backup lights are a Lumina Micro or L&M 500, usually aimed at the right shoulder to check the fence lines for deer. I mostly ride on rural roads and it's pretty common to see several deer between the shoulder and fence lines. The little extra light usually makes their eyes pop just enough to warn me.