I can tell because: a) it's cooler b) I just bought some coloured corduroy jeans that remind me of pumpkins and c) I have that weird seasonal visceral craving to break out the sticks and start knitting.
Knit wips are calling to me as they bulge out of the cupboards - "pick me! pick me!". I also realised I spent a long time thinking about wrist warmers after seeing some on a girl in the whole foods store in town and then, the clincher - I noticed that I slowed down as I drove by the yarn store.
I think it's time to see if I can remember my ravelry password. Who's joining me?