Why is there no air conditioning in our apartments? For that matter, why is there no air conditioning in 95% of vacation rentals or even in entire hotels in Vienna?
This is because the bulk of period buildings are protected and special laws apply to their general appearance. This includes a ban on satellite dishes but also the outside units of an air conditioning system. So that was that: no outside unit, no air conditioning.
Since global warming started to really make its effects felt, weather is unpredictable and there are every year a few days with quite high temperatures (35°Celsius or very rarely, even more) in Vienna. Usually totaling about one to two weeks and generally occurring in July or late June.
What to do? Did you know that we have dozens of kilometers of fine beaches in Vienna and that we do swim in the Danube river? Go to the Donauinsel, the Alte Donau or the Gänsehäufel (my personal favorite) for a swim. Water is generally warm 23-24° Celsius. This is totally out of the beaten track (for tourists, there are thousands of Viennese there...)