[downut]

My wife is an expert gardener, able to do wonders in Arizona at 5500'. She's been working the same plot of land for 25 years. The advance in the last frost day has been quite noticeable. For our plot (up on a ridge, so lows are warmer by up to 10F than the valleys below), it's usually about two weeks earlier. She's still wary, though, as she's lost entire beds of seedlings to outlier cold snaps in late May.

Interestingly, there are animations of the changes in the hardiness zones over time:

https://www.arborday.org/media/mapchanges.cfm

Difficult to argue with that, I think.

[wrycoder]

Interesting, thanks! It shows there has been significant change in the central part of the United States. Not much where I live in NH. And, I would have expected to see more change in California.

Needless to say, this is not global climate change, which is what all the discussion is about.