Allergies, perhaps? 'Tis the season, and Georgia and parts south are notorious in that regard. A bad enough reaction to pollen from some sort of late-summer grasses might be enough to trigger a lowgrade temp. And by the time you got home, similar grasses might have been kicking in up north, thus prolonging the reaction.

Another thing that makes me think allergies might be a possibility is that you better after a heavy thunderstorm, which tends to settle pollen.