A lot of the Northern portions of Central Alabama are essentially right on the line between Zones 7 and 8. The current USDA Zone Map officially has us in Zone 7, but their previous version from the 1980's had us in Zone 8. The new release, if they ever finish it, will probably put a lot of locations back in Zone 8. What this really means is that we're flirting with the Zone 7/8 line! In my opinion, it's fine to grow most Zone 8 plants in our area, but there is a risk associated with that since eventually we're going to see temps. near zero again, and many of those plants will be damaged.

We are straddling the fence ;-) IMO, most properties on the hill in Jacksonville are most likely in zone 8a. We are located 2 miles west of J'ville. Going by experience, we are in 7b.
Hardiness zones are based on average winter low temperatures but there's a lot more that determines the survival of a plant.

Here is a link that might be useful: Plant Hardiness Information