Well I'm still in 8b, but I don't know if the little 9a spot just a few miles southwest of me has always been labeled as such. I used to live just north of Columbus and it's still showing 5b for that area. I am also seeing the little 7a bubble over Akron. Interesting.

Exactly. I find it curious that Akron is supposedly warmer than Columbus.

At least I feel safe growing zone 6 perennials now.

Looks like the dot for Akron (downtown?) is all that's 7b while all else around it is a 6a or 6b. I don't know if I'd put much stock in that.

tj

Actually, Akron's downtown is included, but it is a relatively small portion of the 7a bubble. In fact, my entire neighborhood is 7a now. (Highland Square)

i wouldn't believe it. i think that the new zoning is reflective of urban heat bubbles. but i'd go ahead and plant zone 6 plants and see what happens-- some may do it some may not. of course heavy clay soil plays a major factor too.
i manage a rosemary, up against my house, but it has 6 inches of gravel underneath it.
diggerb

I would think that improved data required a change in downtown Akron's zoning. I'm not too sure about global warming!

The USDA has Actually Released its long awaited and officially revised Plant Hardiness Zone this year on about January 25th. The map also includes interactive data so that you can know the precise annual minimum temperature in winter for a given location.

I think it includes the UHI (urban heat island) effect, buyt I don't buy anything zone 7 for Akron, or, anywhere in Ohio. In fact it seems any reference to zone 7 has disappeared when I look at Akron on that map.

When I zoom in on zip 44308 (downtown) it also says "days over 86F" as "rare" which I don't buy. I guess it depends on your definition of rare, but since 86 is only 4 degrees over the average high of 82, it's hardly 'rare'.

Just looking at Akron-Canton airport (more exurban than the city, but the closest data) the last 10 years winter minimums were:

2002: 6F
2003: -8F
2004: -4F
2005: -4F
2006: 3F
2007: -6F
2008: 0F
2009: -14F
2010: 2F
2011: -2F

That averages out to -2.7F, so that's a mild zone 6 for sure, but the fact that it dipped to -14 in 2010, and, a few times in the 90s even colder, I'd hesitate to plant anything less hardy than a zone 6, or it won't last a decade most likely.

I'm in Akron (North Hill) and I'm in 6b. It seems about right to me, but I've only been gardening for a few years.