Highs in the low 80s. Issued by meteorologist Chris Suchan. Julie Maxwell, Huntersville. Clearly this is not the only summertime scenario, but let's address your observation because there is something to this. To the west of us, as we all know, the terrain becomes higher and higher as we encounter the foothills and then the mountains.
Summertime thunderstorms depend heavily on low-level heat rising into the cooler upper atmosphere.
Low-level warm air is heated by the ground, NOT by the sun's light passing through it. Otherwise, it would be nice and toasty at 30,000 feet, and we all know it is not. In fact, even at 5,000 feet, it is already a lot cooler usually than the surface. It often gets a head start on forming thunderstorms before the hot air at low elevations can on many days.