That saying originates from Greek and Roman times, when Sirius, the Dog Star, aligned with the Sun during July and August and was thought to bring extra heat to the earth. The Dog Days are evil times; seas boil, wine turns sour, dogs grow mad, and all other creatures became languid; causing to man, among other diseases, burning fevers, hysterics, and phrensies.
Bad news, indeed. Add to that; air conditioners fail, general managers become cranky, and transmitters overheat causing damage to sensitive control circuits, which is even worse.
We shall be busy dealing with things like this:
Air conditioning condenser with low refrigerant. This unit either has a leak or was not charged properly. I would hazard the former.
Fan blade on condenser coil failed due to metal fatigue. I have seen this in more than one place.
These wall-mount Bard AC units are pretty reliable, however, even they fail from time to time. The best course of action is to have a maintenance plan, a backup plan, and the number of the best HVAC contractor that can be found.