There is a pretty neat town in the NC mountains called Highlands, I think it's around 4400 feet, and it's where a lot of wealthy southerners would venture in summer.
It's a pretty ritzy town today, no touristy spots, no chain restaurants or motels. Each thousand feet of altitude cuts 4.5°F in temperature, on average.
So, if it's 90°F in Atlanta, add 3400 feet and it's 74° or so.