Air conditioners use a lot of power, and our air-conditioned homes and businesses and factories are everywhere.
Transmission lines have to carry power from these few power plants to many destinations via transmission lines, which are wires with a limited capacity that goes down when it’s hot. When a line heats up it droops, and if it then connects with something else, the line short-circuits and stops working. Which forces other lines to pick up the slack, and if enough other lines become overloaded and fail from heat, voltages can no longer operate at proper levels.
At best, that makes our lights dim and slow down air conditioners and other appliances, which degrades their motors and shortens their life spans. At worst, the power grid comes down and black-outs ensue.
Lewis University (2013, July 19). Why does hot weather cause power outages?. ScienceDaily. Retrieved July 22, 2013