Clearly, a sign of global warming.
But wait, you say. That's silly. You can't make such a determination based on just a day in a week.
Actually, you can. And the U.K. government weather forcasting division has.
Because the only thing that matters is the last 160 years. The 10 warmest of those years have all been in the last 12. No matter the previous several million.
Thing is, this sort of thing hurts their cause, because it makes people like me (certainly a minority) more skeptical.