The UK. In my part the average temperature in June, July and August is 14C (57F). Being an average it can obviously be colder so you need a thin coat similar to the picture.
This is probably an urban myth. There's a story about a Japanese guy at The Open golf in July - probably St Andrews. With the rain hammering down he turns to the guy next to him and says "Why don't they hold it in summer?"
Many years ago, I was in SF in late June. Fell asleep with the window open and woke up with strep throat in what felt like a meat locker. But I've also been there in January with temperatures in the mid 50's.
Caption this Meme 
