Because I have nothing better to do, I decided to look up the temperature in Ohio in June. I picked Columbus since its in the middle of Ohio. The average low in Columbus is 61 degrees in June. Average high in June is 82 degrees.
As a friend of mine is fond of saying; "climate is what you expect, weather is what you get". Averages are just that with the range being ±3 standard deviations.
The small town in Ohio I was camped in on GOBA in the early '90's did reach 35°F two mornings in a row and those who believed the averages and brought a single blanket or "sleep over" quality sleeping bags suffered very noisily.
The point about individual cold tolerance is well taken but most people are better served with a sleeping bag a bit too warm than a bit too cold.