It's pure aesthetics
It's one of those things that chips away at one's beliefs about the human spirit.
I do agree myself that A/C is a luxury in most cases (at least in Paris) and many other things that would help the environment should be done before installing that.
All of France takes a break in August because it's too hot to work. This is only going to get worse with climate change.
What is too hot for you? For me an average a mean high temperature of 25 deg Celsius in August is reasonable (source: https://en.wikipedia.org/wiki/Climate_of_Paris).
I would aim for maybe 95-97% of expected weather to be covered.
(Also, air conditioning can be fully solar powered and in fact has synergistic effects with solar power. And also, making a permanent venue for the Olympics will probably save a lot more resources in the long run, but no one's willing to talk about that.)