On what date is the last frost in Ohio?

According to http://www.victoryseeds.com/frost/oh.html, the last frost date depends on where you are. Some areas vary greatly depending on their proximity to lakes or rivers.

CitySpringFallAkron5/2110/2Athens5/319/19Cincinnati4/2910/13Cleveland5/1810/5Columbus5/910/3Dayton4/2710/16Lima5/199/24Sandusky4/2910/14Toledo5/169/29Youngstown5/249/29