Moving from the US to the UK, one of the first things I noticed was that the colloquial understanding of the seasons mapped much more cleanly onto what actually happens with the weather here. Growing up in the midwest of the US the seasons all felt off in the same way the author describes.
In my mind this is it, the colloquial seasons, and with vague boundaries depending on feeling, whereas the calendar "seasons" are there just to quarter the year artificially.