First day back at work for 3 weeks (hols in France & Cornwall) and it was a lot darker when my 5am alarm clock went off - always signals the start of autumn for me.
Garden's in full swing for the coming months: Holly berries turning red, Rowan trees growning with red berries, brambles turning from green to black, 'Lords & Ladies' popping up, damsons nearly there, hazelnuts getting fatter by the day......etc
Other signs - emails from my coal & wood supplier, local paper full of ads for Christmas lunches/Seasonal Menus - only 149 days until Christmas