Try this link. I havn't looked at it in a while, but the last time I did, I was in zone 7b (Conyers, GA), so Atlanta should be about the same....Maybe what you are seeing the zone 4 on is a "heat-tolerance" map? I've been seeing different maps when looking up unusual plants lately which tell you cold hardiness and heat tolerance.

Here is a link that might be useful: Zone Map

Old map it is 7b; new map 8A. Probably a true borderline area between the two...the north side a warm 7b and the south side, off of the Atlanta Plateau, a definite 8A.

thank you both for the info! I looked on the hardiness map and it looks like zone 7b. I guess it won't make much difference if I am just a bit EAST of Atlanta, in Loganville, will it?

Sixcats, you are probably just slightly cooler, 7b is probably correct. I am in downtown Atlanta, and my neighbours and I are guessing we are at about 8b due to reflective heat, our proof is in what we are successfully overwintering....

GGG

"slightly cooler" sure sounds good to me after the heat we've had lately!! My azaleas ---I've had to give them ground water in their mulch daily to perk them up and try to keep them "cool". If it's bad NOW, how bad is it gonna GET?? I'll take ANY "cooler" zone!! Thanks!

I can tell you from my records going back to 1997 that temps have been true zone 7b only once(minimum of 0-10F), rest of the time 8a and warmer.

Alan, I must agree with you! The temperatures here are definitely "warmer", even when they are supposedly "cooler"!! Maybe the "zone" is 8a, temperature wise for heat tolerance, and 7b for cold hardiness? Is this possible?

Sixcats, I think what Alan is saying is that since '97, Atlanta hasn't gotten below 10 degrees except for once. The zone map (one of them anyway) says 7b is 0 through 10 for minimum temps.

I feel like a lot of plants aren't listed correctly anyway when it comes to zones....I successfully over-winter I few things here that are listed as only being hardy in zones 9 and above.

the "hardiness" map shows I'm in zone "7b". The "average annual freezing temp." shows I'm in zone "8a"! Which would be the most accurate as of 2005?

Sixcats, you have learned the beauty of microclimates. You may find that part of your yard is fine to zone 7b, and other parts can overwinter other plants, such as Wildflower has found.
For example, I find that in areas that are sheltered from winter rainfalls, I can grow very warm and tropical climate plants hardy in the ground. The key is to keeping winter wet out of the root system of many of these plants so they don't freeze.
At church I planted coral vine and hawaiian woodrose last year. Both have come back with a vengance because the roots were kept dry. On the other hand, you may find you lose plants in the summer due to the combination of heat and humidity. It's just not all that straight forward.
Just keep observing your garden, and you'll learn what does well where. And also just keep asking here. Asking about specific plants on this forum has saved me a lot of dead plants!!

GGG

Thanks for all the help, everybody!
GGG, I don't think I LIKE "microclimates", ya know what I mean?!!! I have enough trouble with a few azaleas, some in warmer "spots" than others! Thanks for the info, though---I can use all the help I can get!!