many of those old buildings have balconies where you can hide AC nobody from street can see, personally I have my multisplit unit on the roof (I'm on top/5th floor), same with neighbor floor below just with longer pipes

it certainly more than 4 weeks hot enough between June-September to justify AC, even one month per year is comfy + it helps also during heating season if they start too late or end too early, you can use AC for heating as well