I love hot weather but 40c and above is a bit much and would prefer temps of around 28-32c.
I went to Las Vegas a few years ago in June and they where having a heat wave with temps of 112f / 44c and it was like being in a oven, due to having mild asthma i found it hard to breathe at times as the air was so hot and dry.
On the day i went to the valley of fire the forecast was for temps of 111f but the tour guide who was driving said his car thermometer hit 117f/47c which was pretty uncomfortable as the air con wasn’t the best and started feeling sick from the heat.
I am looking forward to seeing if any records get broken but at the same time i think it could be pretty unbearable for some people.