I don't know what the case is in your countries, but in mine it's natural that during Summer and more specifically during August, a lot of people are leaving the big cities for their summer vacation. The only incoming ones are the tourists. Now these past 2 years i have decided to stay in the city instead of going for my summer vacations at this time.
Even though going on vacation is to another town or to an island is amazing, i've realized that during Summer is the worst possible date for someone to go on vacation, at least in my country. Most of the people are taking their leave days or forced to take their leave day during August, so there is a massive number of people travelling to basically the same destinations.
That leads to massive traffic, to not finding spots to park, and in general overcrowded small towns, islands, cool places, cafeterias, taverns and beaches. To add to that everything is way more expensive than it should be and you basically don't actually enjoy your vacation that much.
At the same time big cities are empty and that means, less traffic, park spots everywhere and quiet. To give you an idea, it took me 20 minutes by car to go to a cool place to eat, which on any other date takes me like 1+ hour.
People seem a bit more chill, as you don't have to wait long hours in traffic and thus you are not that annoyed or angry. Ofc it's not like the city is completely empty but let's say that if the population is 4-5 million people, then during August there are 1-2. Still, you can easily tell the difference.
The way things are all, the people have basically moved into 1-2-5 big cities to find more opportunities, better schools and hospitals and in general to make their lives a bit better. As a result, the rest of the towns and villages are like dead places. I blame politicians and their action that we are in this situation. I know a lot of people that would move out to a smaller town if more jobs were available, or if there was a hospital nearby.
All in All August comes to an end, everyone is again back in the city and i am already waiting for next year to come!