Heat waves would occasionally impact my regular DCA-MCI flights back in the '90's. US Airways 737, flying almost to the edge of the DCA perimeter at the time.

It usually took both high heat in DC plus some weather along the flight path to KC, but about once a summer my Friday afternoon flight would take on a light fuel load and then make a pit stop along the way.

To this day, this is the only reason I've ever been to SDF.