No duh. According to Wikipedia, the autumnal (or September) equinox occurred on September 23 at 3:09 UTC. So 'upon us' is a bit of an understatement. Strangely, however, because of living in the city, being so absorbed with work, and warm weather (until just recently), I hadn't noticed.
I finally noticed on Saturday, when I drove out to the suburbs to see my dad. Because I left the urban confines of Philadelphia and drove along the river, then through Fairmount Park, and finally out into the suburbs along Montgomery Avenue, I finally got my first memorable eyeful of fall foliage. Combined with the crispness of the air this weekend, and it finally felt like fall.
This is a big deal, for me, mainly because I haven't experienced what I consider to be autumn for, oh, ten years now. Six autumnal equinoxes in Houston, where there is no real change of season, beyond going from "ass hot" to "not hot", and four in Switzerland, where the change is, at least according to me, so far less dramatic that it practically goes by unnoticed (at least until I think back and reflect on it). To end my little ramble, fall is my favorite season, and I am glad that (a) I finally noticed it happening, and (b) that there was something beautiful to notice.