Nuclear fission reactors of the type commonly used today require huge amounts of incoming fresh water in order to control the temperature of the reactor. With atmospheric temperatures rising, so are the temperatures of surface water that is drawn into power plants. Since the cooling systems are designed based on a minimum temperature difference for a given flow rate, if the water temperature is rising they can't adequately control the reactor.
During the French heat wave in 2003 seventeen plants had to be shutdown or slowed because of high water temperatures. As the demand for power increases with the electrification of vehicles we will need to develop alternative power sources such as solar, tidal, wind and geothermal that don't rely on fuels and are less dependent on cooling.