Is there a thermocline? Once water warms up over 75 degrees or so I use my electronics to try and locate a thermocline. Then I'll try to fish structure/cover that intersects with the thermocline. I don't think this is a cure-all approach, but it gives me a place to start when fishing warmer water.
Years ago (early 80's) there was a fisheries biologist from the University of Oklahoma - Loren Hill. He did quite a bit of research into bass color preferences and water preferences. He believed, and had quite a bit of research to back it up that the single most important factor in fish location was water PH. I remember reading some scholar-type articles he wrote about defining a PH cline, which is like a thermocline, but a distinct change in water PH as opposed to temperature.
He went on to market the Color-C-Lector and the Combo-C-Lector with Lake Systems, Inc. I heard Loren Hill speak at a fishing seminar a couple of years after the Color-C-Lector hit the market. He talked about how he wasn't in charge of marketing, and how the unit had been, in a sense, marketed under false pretenses.
The Color-C-Lector didn't define the fishes "favorite" color. What it did tell you was what color was most visible to fish, given the water color. The primary problem with the Color-C- Lector was that it was too precise. Given 3 feet of visibility, 8 feet down over weeds it would read one color, move 30 feet and now you're 8 feet down over pea gravel and it is reading an entirely different color. It was very frustrating, and as Loren Hill pointed out, the color that bass could see best, given the water clarity wasn't necessarily the color that bass would most readily strike.
The Combo-C-Lector was the basic unit combined with a PH meter. The idea was that you would slowly drop the probe until you noticed a significant difference in the PH. Right at this moment, I don't remember what the "preferred" PH was. All I remember was that the unit was a pain to use, it was slow to deploy and there were many things that effected the water PH in any given location. (wind, time of day/sunlight, algae concentration, just to name a few)
Anyway, the point of this rant is that your question has motivated me to go back and re-read Loren Hill's research.
I'll report more on that later. Anyway, what I do know is that water temperature isn't the only factor in play here. Water clarity and PH also play a role, but I don't know exactly how they all fit together at this moment. Something to think about and research.