Now that I'm a farmer, I take an interest in something called "hardiness zones" which tell me how cold it can get where I am planting and what will and will not grow there. I never knew what zone I was in until recently. It seems I am in zone 6. But here's the thing: a couple of years ago I would have been in zone 5. In 2006, they changed the zones, because some places had warmed up so much. I found a nifty, but worrying animation of the shift in zones from 1990 to 2006 here. Check it out. It kinda gives me the willies.