A pair of articles look at the start of Summer and the forecast heatwaves. The first article actually notes that the Bombardier CRJ may not safely operate above 118 degrees Fahrenheit; this common regional feeder, used by American, thus has to be grounded at their Phoenix hub.
Click on the image below for a scrollable view; the PDF file may be downloaded.
Aviation is thoroughly dependent on fossil fuel consumption, and is the fastest way that each of us can contribute to record-level (and still growing) atmospheric CO2 concentrations. And, importantly, hubs greatly increase fuel consumption, because more passengers fly longer distances when transferring at hub airports not on the direct route of flight.