That's good info. Very possible she may have hurt herself as she had a few hard falls. Yes, I have read that panting is not uncommon. She is a husky and we are in Winnipeg so 28 today, 31 tomorrow. We have the air on high though and I have a fan running where she sleeps.
Barkingdog, vestibular disease happens suddenly in all aged dogs but more often in seniors. There is a vestibular apparatus in our middle ear that controls balance. Although it can be caused by infection, tumors, in most senior cases it is idiopathic meaning there is no known cause. The current theory are that the calcium mineral crystal in the ear move and that causes a loss of balance so literally the dog has no idea what is up or down causing them to stagger or fall, nausea and dizziness. There is also rapid eye movement which I think is caused by the dizziness as the brain is firing off too many signals. The mineral crystals are sending these signals to the nerves which in turn is trying to tell the brain you are off balance. This also happens in humans but our poor dogs don't have an understanding of what is going on and they tend to also have symptoms of anxiety. Generally, symptoms resolve between 1-2 weeks but some dogs may always have a slight head tilt.