Activity patterns of bats are known to vary among nights, seasons, years, and geographic regions, but the underlying reasons for those patterns are poorly understood. Our objectives were to assess the temporal variability of bat activity during autumn in central Georgia, and to evaluate the influence of barometric pressure and nighttime temperature on nightly activity using Akaike's information criterion and regression models. We recorded 43,168 bat calls and 5839 sequences using an ANABAT SD2 detector during 65 sample nights (4 September to 11 November 2011) at a residence in Barnesville, GA. The number of sequences recorded nightly ranged from 3 to 551. Nightly bat activity was positively related to average nightly temperature and average nightly barometric pressure. In contrast to our expectations, bat activity was not related to changes in barometric pressure prior to or during sample nights. The positive relationship between bat activity, temperature, and barometric pressure may be related to the energetic costs and benefits associated with flight and prey availability during autumn in central Georgia.