Just west of Charlotte and southeast of Asheville lie North Carolina's Rutherford and Polk Counties. In this two-county region one will find what's referred to as the "Thermal Belt Region/Zone". The thermal belt region is an area in NC that will often have a temperature inversion which results in milder temperatures for the thermal belt zone.
In this region, there is a somewhat longer growing season, and that has been good news for North Carolina's wine industry and our states apple growers. The thermal belt is a phenomenon that occurs on the southern slopes of mountains and foothills, protecting them from frost and freezing temperatures. The land can't be flat, and it generally has to be a mountainside for this to form.
Heat is absorbed by the ground during the day, and the heat energy radiates up from the soil at night. As the warm air rises, the radiation of the heat causes the air closest to the ground to cool.
All in all, a longer growing season can be found in these areas that have thermal belt development. Because of the phenomenon, killing frosts are held until later in the fall, and they are generally over earlier in the spring. Frost can damage grapevines and other plants but with the thermal belt, several rounds of plantings can take place because of the extended growing season.