When you look at the map at the top of the article, drag the "scrubber" just below the map to compare the current USDA's map (1990 data) to the National Arbor Day Foundation's map (2006 data).

I've heard there are inaccuracies in the National Arbor Day Foundation's map, but there's no official new map to compare it with.

I think the USDA needs to step up, but instead of just averaging the data, I think they should weight the data with the current data counting more than the old data. That would give the benefits of a larger amount of data AND more accurately reflect current climate.

I agree with you, brandon7. Judging by the equations in the article, I estimate a 7a/7b line around Athens/Cleveland. Interesting note: not all areas of the country appear to be warming as rapidly as the south. Areas of the midwest/plains appear to show much less delineation.