And that is what you should be doing, Gandle. It's been my business for the last quarter century to know weather, my profit margin depended on it. I went right to the Government site to see their explanations of the changes. It does NOT reflect warming trends,even though there are a lot of websites who jumped right on that bandwagon. The official government site states it does not. It reflects better data and better record keeping.

IOW, the change is in the number they assign, not necessarily the actual conditions. It also helps to know how that number is derived, and it has to do with the 'average' coldest points and that can certainly mean it doesn't reflect how cold it can actually get and there will be as many cold 'cold' days under that point as over it. It's not going to change how and what I plant either. The extremes haven't disappeared.

It always has been just a general info and does not take in consideration your local condition, heck, it can change between front- and backyard, depending on amount of sun and as in my case, prevailing winds and elavation.

Yeah...."A rose by any other name...."
But in view of global warming we will see more extremes, however I will continue to plant stuff that will die in a severe winter....and be glad for the years it survives.
Still remembering that winter some 30 years ago when the hedge that hid my deck from the neighbors died to the ground! I kept waiting for it to leaf out!

Yup, I am now zone 6 and I don't believe it.

According to the article in the Washington Post, the changes are based on data from the past 12 years. The data was gathered from many more sites than the previous base (which was gathered 22 years ago). It is solely for cold hardiness and doesn't consider possible changes in heat.

The mountain house was and remains solidly 6a, but down here the barely 6b was rezoned into 7a. As anneliese points out, in reality that depends on the specific site. My back patio and veg garden area is surrounded by house and then trees and tall fencing. It's been reliably 7a for decades and now would meet the criteria for zone 8; that doesn't mean plants with a maximum hardiness for 8 can be depended on to survive every winter -- but it would take an exceptional cold spell to kill them. OTOH, the front yard is much colder: open and facing north, in the past few years I've lost shrubs rated for zone 6 and even for zone 5. Which isn't going to stop me from trying them again, lol.

So far *this* winter, we've had three nights that cooled to the high teens, and maybe 5 more that were below freezing. Climate warming or normal chancy variance, I don't think there have been enough cold-hours to meet the requirements of the pear trees. February may be cold enough, but the norm is that Feb throws us one or two snow storms and then starts to warm up. I may have to search for an organic orchardist.

No, the data on the new map has been collected using a thirty year interval to make it less sensitive to shorter term cyclic changes. It is also using, for the first time, GPS data to provide readings where weather stations did not previously exist. The official site, when I checked it yesterday, said the difference in zones was reflective of data and record keeping changes, not proof of warming. It's pretty obvious weather change is occuring, but the two maps cannot be compared directly since the data retrieval is not taken in the same way.