Oh no you’re gonna trigger the Germans.
Nothing unique about Germans in this case, sorry. ;)
So once it is too hot, just turn the AC on and you won't get sick or risk a heat stroke either.
We'll come back to this in several months for a winter freeze to see if Europe has basic heating to keep themselves warm (or will they not turn the heaters on for some reason) and in a year, to see if the rest of Europe have learned their lesson to just have basic AC installed for the next heatwave.
Personally I think their "allergy" is just because most AC units in Japan are disgustingly moldy and never cleaned regularly.