Hey all:
Up here in Northern Ohio, I find that the flatheads start moving around 50-55 degrees. In this neck of the woods, things don't start happeningg til around early to Mid-may, depending on how much rain weve had and wen the thaw took place. I know some guys have said they catch them in April while fishing for walleyes, but I have my dobts, maybe just foul-hooked. I guess you have to just expoeriment with your location and local waters. Good luck.
Andy