In late July or early August, there always seems to be a day when, all of a sudden, I can feel fall approaching. I could feel it strongly in Boston, where the air would pick up a bit of crispness, if only momentarily. I also felt it in California, but it would manifest differently, as a stillness in the air and a bit of humidity. I don't remember noticing it in North Carolina. Perhaps I wasn't there long enough to get tuned in to the weather patterns, or perhaps it was less obvious due to the humidity. Today I felt it here in Ithaca. The air was crisp, there was a breeze, and even the light looked different.
It's strange that it always seems to be at the same time, regardless of location. I notice the transitions between other seasons, of course, but for some reason the first glimpse of fall is the one that is most subtle and yet the most obvious.