It’s confusing, at least where I live. The fall begins here on two different days. If we hear the weather forecast, they cont already the whole month of September to fall. Of course, it’s often getting already colder in the mornings. But luckily, the temperature is not the only definition of a season.
In astronomy, fall (or spring) begins on this date, when day and night are of equal length. This year, it’s on Friday 23th of September. Using this kind of measurement makes sense because it has a natural origin. The same comes with summer or winter when we have the longest or shortest day.
I wonder where the same situation is everywhere, where the seasons start on different days.