In the cool depths of a limestone cave, temperature, humidity, and darkness are constant — ideal conditions for hibernators to save energy over winter. Endangered little brown bats (Myotis lucifugus) may hibernate for up to eight months, emerging in spring with minimal stored fat. Exiting the cave on warm, calm days with higher insect activity could provide an opportunity to forage and recover from hibernation. But without weather cues from the outside world, how might hibernating bats anticipate good conditions for emergence? Atmospheric pressure changes, which precede warm and cold fronts, are sensed by many animals, and little brown bats appear to synchronize activity during hibernation with pressure patterns as spring approaches. Using infrared cameras and radio telemetry, my research monitors the activity of bats throughout their hibernation at a Manitoba  cave to reveal how air pressure and weather influence their emergence timing and behaviour.