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Amazing how much most of the country has trended up a zone. Not sure what could be the cause and I don't want to start a political debate on here.

I believe i read when the refigured them, they were using the last 20 years' worth of data to come up with the numbers. I certainly have noticed that in the 16 or so that we've been here it was more of z 8 lows as opposed to z 7, so i can't say i was surprised when it changed officially. Whether it's normal cyclical fluctuations or greater overall change i won't touch, but there's no denying it's been warmer for 20 years, whatever the reason.

I think if you factor in all the trees taken down and all the roofs erected as well as new roads,acres of concrete driveways and paved parking lots that's a ton of new heatsinks.

I grow some zone 8 plants and they do well, but I site them carefully. A cooler season could be their undoing. While I claim 7b I am all too aware that it would take only a degree or two to make a big difference in what I can grow -- either warmer and cooler.

Some NASA data is trending to cooler, enough to undo the warming we've experienced. For instance, the oceans are not actually warming up - which runs counter to what they've been expecting. When I was in junior high the scientific community was forcasting a new ice age - scared me big time as I hate cold. I still have Time and Newsweek magazines with extensive articles on the subject.

The weather systems on this planet are incredibly complex and are timed in decades, each piece playing out year over year in a slow unfolding, the influencing factors in the billions.

Very true Jody, it's a very very complex planet and the cycles and weather systems are very good examples of exactly what a complex machine Earth is. The science of weather, climate and the environment is very facinating. I love watching some of the science channel shows/specials on it. No political debate to start here either, I just wish science would report science, and let all the politicos go fight it on some other front! Mother nature is a beautiful and complex lady.

One thing that makes me skeptical of these new maps is that last frost for Zone 7 is generally April 15th, right?...well, we had that last night here in the "new" Zone 8. I think you guys are right--Mother Nature is too complex to try to really predict. I've read about how people have had success with Zone 9 or 5 plants here as well.

I guess the "zones" are really "best educated guesses"?... =)

I would have to agree that the new zone maps are more accurate, at least considering the past 20 years or so. The problem is that all it takes is one cold snap to cause a lot of problems -- as a lot of gardeners found out with the hard freeze of April 2007. However, it has been a very long time since the coldest winter temperatures dropped down to 0 F in the Triangle area.