May in Virginia, West Virginia, Ohio, Indiana you can easily get 40s at night. Likely upper 40s. June in Illinois, Missouri, Kansas, east Colorado expect lows of 50s likely.I can tell you from personal experience that overnight temperatures in the high 30's have occurred in mid-Ohio in mid-June.
Yes. If you look at the record temps for most places you will likely find highs of 100+ to lows of -50+ for almost everywhere. It hit 70 degrees last week in mid Iowa. I rode my bike. Unfortunately, or fortunately, that is not the normal temp. Your high 30s in mid Ohio in mid June is likely a once a decade event. Not something I would use for planning a ride. In mid June in mid Ohio the average low at night is probably 50-60. Highs of 60-70. Give or take 5-10 degrees either way. I'd use that for planning.
And you are also forgetting the seasonal effect. You always think things are colder than they really are in summer because you are used to hot weather. And in the winter you think things are warmer than actual because you expect cold. A friend stopped by yesterday on a bike ride. He said it was 45 degrees or so. I looked at my thermometer and he used an app to get the temp on his phone. It was really 35. I walked outside and it felt warm and pleasant but still cool. I might have guessed it was 40 or so. But it was only 35. In February you expect cold weather. 3 degrees above freezing seems warm.