Overheated airliner?

An unusual experience last month. We’d boarded our Delta flight from Charlotte to Atlanta, had been pushed back from the gate, were awaiting takeoff. It was a very warm day outside (perhaps 100 F) and inside the plane it was also becoming uncomfortably warm. The pilot said to be patient, when we got airborne we’d feel cooler. Then ten or fifteen minutes later he announced that we were not flying, we were going back to the gate because this hot airplane was not fit to fly.

I’m curious, while the heat was becoming uncomfortable on the runway, why the abrupt abort? Any thoughts? I can’t remember the aircraft type, perhaps an MD 80. It was a single aisle, three seats on each side plane.