I assume you don't live in / know about the situation in France. Here most of the nuclear fission power plants are down because during the heat wave the rivers have dried up and don't provide enough coolant anymore. Yes, they are all under maintenance / being repaired as well, but that is because they aren't operational anyway so why not use the time to do what has been postponed for too long. No one in their sane minds would take down half their power plants for maintenance simultaneously. Also, nuclear power plants do not just stop producing energy when they are down, they even consume some.

In other words, nuclear fission power plants are not the solution, they even make the situation during a heat wave worse. I wish there was a silver bullet, but I fear this is not it.