Question: What has greater impact on water temperature, falling air temp or less sunlight? Kinda wondering now that air temps are high, but fewer hours of daylight.

Loss of length of day allows temps to fall more at night. I'm quite a ways north of ya but I'm down 12 degs already at 70.

If I had to guess in a general sense... I'd say the lack of sun light makes a bigger difference. My pond surface water was at 83.3 degrees F yesterday at 1pm and the air temp in the shade was 78. At about 4:30pm my pond is in mostly shade and at 6pm the air temp had climbed to 86, but my water temp had dropped to 81.9.

Side note: the water temp at 18"down had climbed from 75.4 to 76.5 over the same time period, but I'd bet it was dropping as well.

That's my general sense example, but let the difference between water and air temps get more extreme and the effects should become more pronounced and the sun takes a side seat... At some point convection heat transfer (air to water) has more affect than radiant heat transfer so long as the temp difference is big enough. Don't forget the angle of the sun (season) affects the way the light heats thing up too.

Thanks for responses, guys. Helps me to think through when I should start fishing again, especially for HSB, and when stocking might be advisable.

anthropic, this is something we look at-among other things-to help decide when to start fall test netting.
When length of day gets close to 12hrs (sunrise to sunset) this seems to trigger many species to start their movements and step up the process of, dare I say-feeding more aggressively. Obviously water temps, weather, etc, all play into this but we've pinned it down to a good reference if nothing else.
As you well know, photo period affects/triggers many instinctive actions to kick in on many creatures, fish included.
I also oversimplified my statement above about length of day in my post above. Water temps do not drop just because of cooler nights but also less solar input (energy transfer). Interestingly, when night time temps start dropping well below water temps, there can be "almost" as much evaporation as there is in hot summer weather. Now, this may not be the case in east TX, but here in the central parts we can have water in the 60's and nights dropping to near freezing..It flat sucks the warmer water into vapor. That was FYI, not really on topic there :-)))