They're everywhere in north Georgia now. They can be spotted early in the season, but they're tiny and inconspicuous. By August or so, the successful ones have gotten big, and some get very large.
As the season shifts into fall and the nights become cooler, the Joros seem to be a little more resilient than the native barn spiders, which re-build their webs each evening at dusk to catch night-flying insects. Cold nights = few bugs. The Joros, although they stay in their webs at night, seem to primarily hunt during the day.
Eventually nights come along that are too cold for them. I had a very light frost in mid-October, but it was very borderline. They were fine. Nights in the low 20s are a different matter, and in early November we've had a couple of those. They're now mostly hanging dead in their webs. They've laid eggs by now, so the cycle will begin again next spring.