Businesses open to the public and offices almost universally have AC, though, except maybe for mom and pop shops, so you definitely can go to the mall or the movies to get some fresh air.
The best place to go during weather like this is actually a grocery store: Picard, which only sells frozen food and so you get the escaped chill from the freezers.
This has worried me since I was a child. If everyone has AC it's a race to the bottom as it gets warmer and warmer, AC has to work harder, using more and more energy etc. You end up with hellhole cities where you can't be outside at all. It's simply not sustainable. We have to do other things like having green spaces, less tarmac, shutters on windows etc.
[0] https://www.euronews.com/green/2023/08/30/fact-check-is-air-...
Localised to alleyways etc the effect can probably be even worse.
The night time re-radiation has the effect of bringing the min closer to the max readings, and so making it look as if temperatures are going up, even when max temps aren't changing much. The same effect can't be seen in rural places where there's less tarmac.
Installing AC is actually not allowed in many places ( because of urbanism laws)
Only possible AC is those single hose mobile units which are wildly inefficient and close to useless while burning energy.
FWIW at least in the US (and I can't imagine they wouldn't be available worldwide) there are also dual hose portable AC units which can perform fairly decently, at least far better than single hose. I needed to use one for awhile at an old office (I think it was a Whynter model) and it was effective. There are also more exotic portable units that use water as the fluid dump, but that requires having a sufficient water source that you can utilize, and probably isn't going to be doable in a residential unit in a city. We had a couple at the chemistry lab I worked in 10-15 years ago that hooked into the lab water lines.
If you are worried about the local heat generated by the air conditioners themselves, there are new coatings and panels that can radiate that heat directly to space, for example https://www.skycoolsystems.com/. Also just removing a few parking spaces and replacing them with green space can help at a city wide level.
That's also only the operation of the things, their production and transport involves global chains of mining, shipping etc. and all the solar panels would be the same on top of that
Compare with data centers running entirely off grid, powered by tens of massive gas generators.
In Florida, HVAC accounts to 40% of energy bill of the household.
40% of 15% is not that much, even if everyone is using AC.
Just because you can make it look small by focusing on the percentage doesn't change that. At the end of the day it means, if we accept these numbers, that the total national energy usage would go up by around 7%. That then gets multiplied across France Germany, The Netherlands, Poland, Belgium, the UK & Ireland etc., to the point that the total power usage is as if we suddenly had another entire country.
And keep in mind while considering any of these numbers that our current 100% is already much higher than where we need to be at to avoid widespread ecological disasters. We need to be reducing our usage not saying "well it's only a few percent more."