Me and my nephew did an overniter on Broad River Trail in Stephens County, Ga. Really beutiful trail. 7.4 miles in and out. Nicest trail I know of after Panther Creek that is relatively close to the Atlanta area. Really hard to find. I checked out weather.com before I left and it said a low of 40 was expected for the nearby town of Clarksville. I had 29 degrees on my zip thermometer at 6:25 a.m. Like Pan said, prepare for temps 10 degrees colder than expected.
In my experience, this is ESPECIALLY true in the Mt. Rogers area. I have been several times, and the weather is ALWAYS cooler and wetter than what weather.com forecasts. BD