I live on a hill about 1-1/2 miles above Meadville, PA. I was always under the impression that my Zone was 5B but just checked out Meadville, PA zip 16335 in Zone Lookup and find that it is listed as 5A. The average temperature difference between the city of Meadville and my hilltop is about 5 degrees F (lower on top of hill.) In winter it could be peaceful and calm downtown while on top of our hill we're having a blizzard. Also it gets very, very windy on the top of the hill where I live.

Please clarify the difference between Zone 5A and Zone 5B and your thoughts about whether my home might be 5A or 5B. Thanks.

I'd think your's should reflect the colder zone but the demarcation line might not consider attitude as it's not mountainous there, just hilly. Is your location south of Meadville? That might factor in even though it's only 1.5 miles.
Zone lines fluctuate periodically, they're not set in stone. I've seen my locale go from 5b to 6a then back to 5b. I think the 6a is more correct and just go with that.
I sincerely believe the world is heating up and admire Al Gore.

jmorth - my home is 1-1/2 miles north of Meadville and I believe my zone should be the colder of the two - 5A or 5B. Being a dumbie, I don't know which of the two designations is the colder. Please enlighten me. I sure it explains it somewhere, but I don't know where to look.

5a would signify colder

5a would signify colder. You're thinking your precise location should be a colder zone than Meadville? if so that would go to 4b. +/- 5° probably factors into sub-zone placement (the letter after the number). Zones by only the number (without any letters following) are based on 10° differences.

I guess I'll change my zone to 5a as the town about 5 miles away at the same elevation as me is listed as 5a also. Appreciate your help in explaining the difference between "a" and "b" designations. I'm now in my upper 80's and not so peppy and spry as I used to be. I don't have many perennials any more and have mostly annuals in patio containers. We have early fall frosts and late spring frosts - so I usually time my gardening around those dates. Don't know why I waited so long to pin down my zone
now that it's not so important as it used to be, but you've answered my question very well and appreciate your help.

Your welcome Don, upper 80's - fantastic.

Don, Jack is definitely correct with regard to 5a being colder than 5b (just think about the overall zone thing... warmer is higher numbers)

But there are so many microclimates that the zones really can't address. And then a few years ago the USDA revised the map and moved a lot of us to a warmer zone than we had previously been in, which, in my opinion, is just so much "horse hockey" in the words of the Colonel on MASH. They can say I'm in zone 5a all they want, until we get a winter like we had a couple of years ago... then, 4b might be a stretch.

Sandy - so true! Just like listening to the weather forecast - which one? - they're all different - at least around these parts. Last winter weather was beautiful - already hearing vastly different versions of what to expect this year. Remember the song "Que Sera Sera" - "Whatever will be, will be."?

Ah, don't get me started on the weather forecast -- our "local news and weather" now comes from Marquette, which is about 65 miles north of where I am, and on Lake Superior as opposed to "my" Lake Michigan. Their weather forecast doesn't differentiate where in the Upper Peninsula they are talking about... so basically it is useless to everyone!

Sometimes it's best to just look out the window and check the outdoor thermometer...