You're right, what I can glean from NOAA's Climate at a Glance isn't an exact match to record high
summer temperatures. One of the posts responded to was for growing seasons. The claim was that
longer "Frost-free Seasons Increases Stress on Crops" and of course, Is summer just June through
August or is September 21st the last day of summer? Growing season, meteorological summer
astronomical summer, Frost-free season. What I've found out is that summer time Maximum
Temperatures in the United States have cooled for most of the country since the 19th century.
Winter Maximums on the other hand have warmed up. The dividing line between those two statistics
is May - October and November - April. In actual fact United States weather patterns have become milder.
The folks on your side of the coin complaining about extremes in weather as the new normal are going
to have to start complaining about extreme mildness.
Here's a map of what that looks like:
Most of those states shown with cooling summer MaxTemps for over 80 years have been cooling since
1895 when the Climate at a Glance data starts. I assume the phenomenon has been occurring for
some time before that.