Lake temperatures for Ohio inland lakes aren't anywhere to be found. I looked for quite a while with no luck last week after I saw your post. Anyway, don't forget that water temps do vary quite a bit from one part of the lake to another. Currents, lack of current, sunny side versus shaded, water depth all affect it.
On using a single number to guide plans and tactics. Surface temps are just that - they do not indicate temps at depth. For instance, a shallow bay is likely to hold surface temp down to the bottom and be very warm and productive early in the spring. But a channel or drop-off might be 10 degrees colder at 6ft depth. And the overhead angle of the sun from early spring to summer changes - low in the south to direct overhead summer, and that heats up one side earlier than the other. So, having a single number on any given lake for surface temp is of some value. Knowing exactly where that temp is taken, and understanding how the lake micro-climates relate to that single number is a key.
I believe that atmospheric history is more relevant on identifying the peak of productive periods. Lunar is the most obvious of these. Here is the most comprehensive weather database toward that idea. http://www.wunderground.com
The link below is the almanac from that site ("Weather Underground"). Temps, precip, lunar, and much more tabulated, charted, graphed and summarized. It would seem that analysis on these data put together with a long history of fishing experiences ought to help point to hot time periods and prioritize tactics. But water temps are not there. And we might need another Einstein to figure out how to use it. http://www.wunderground.com/history/airport/KDAY/2004/7/4/DailyHistory.html?FULLALMANAC=KDAY