There is an official start date for autumn, I guess several of them. 1st September. Date of Autumnal Equinox, that sort of thing.
To me however, there are several more unofficial ones that are actually more meaningful. For example, as I left work yesterday, cycling along towards the scrubby patch of ground, a familiar flutey piping double whistle pinpricked my eardrums.
The first flock of Pied Wagtails of the cold months. You see them in ones or twos throughout the year, but flocks, well, that is a sign of autumn.
An even more certain indicator as the one I had when I went running this morning. It was bloody freezing, and the blue skies that had tricked me from my living room window suddenly disappeared as heavy rain came down, blown on an icey wind from the west.
But even then, there are still things hanging on in. A lovely vivid orange Comma butterfly fed off my butterfly; red admirals still show black and red against the grey. And at night, the summer triangle is still visible.
Hold on to them as long as possibe, just hold on.