I'm in London. It's sunny and 21degrees, my car says so! I'm wearing a thin, long sleeved top. Virtually everyone I've seen is wrapped up in thick coats, scarfs and hats! Why?! If it was 21 degrees in July, you wouldn't dress like that. I really think people just decide, well it's October, I must wear a coat rather than making that decision based on the actual weather... don't you think?