There used to be some grafitti near where I grew up: "summer's here - let's riot"

Ah ha ha. That's true of London. I seem to remember that grafitti, is it in Notting Hill?

I think generally people were more concerned wsimply with survival in winter - keeping warm and fed during short winter days.

True. I was going to make that point - that cold and hunger can make people more apathetic. The Russian Revolution rather scuppers that theory though, March and November must be rubbish times to hang around on the streets of St Petersburg.