Defining autumn

How do you tell that it is autumn? Is it falling leaves and temperatures? Adding extra layers of clothing? Thinking of Christmas?

I know that it is autumn when:

The crows start to wake me up before daybreak.
The guavas ripen (not unrelated to the crows' revelry).
It's the Marburg Show.
I have to add a morning sweatshirt to my t-shirts and shorts.
It's dark when my alarm goes off.
The children don't want to get out of bed in the morning and neither do I.
I can't see my monitor clearly in the mornings with the sun on its northerly trek shining straight in the office window.
It's a long time till Christmas.