Bats are one of the most widespread and speciose orders of mammals. Despite their huge biodiversity, little is known about the natural behaviour and ecology of many species given the difficulty in monitoring and studying them. Pipistrellus kuhlii is one of the most common bats of the Mediterranean biome but its ecology remains ambiguous given the scarcity of longitudinal studies. Such basic information is urgently needed to predict the shift of species distribution range under climate change scenarios. Here, we analysed the effects of weather variables (namely temperature, precipitation, wind speed and air humidity) on the body conditions of P. kuhlii monitored in five maternity roosts in Southern Europe over more than a decade (17 years). Using linear mixed-effect models, we disentangled the impact of weather predictors on body condition variations in 347 individuals. Our results revealed species-specific sensitivity to variations in the monitored four main weather parameters. Through the modelling analysis, we show how weather seasonal variables recorded prior to the capture period had a substantial role in driving bat body condition. A combination of warmer spring-summers and cooler winters was found associated with optimal body condition in P. kuhlii. Our analysis also showed that P. kuhlii bats were favoured by higher spring humidity combined with intermediate precipitation and humidity levels recorded during the summers prior to the capture. The latter parameters (precipitation and humidity) were arguably linked with the proliferation of entomofauna on which bats feed. Additionally, we assessed the body condition of 45 bats that were previously captured and tagged either with bands or PIT-tags, two of the most widespread marking techniques for bats. We showed that bats carrying a ring (band) or a PIT-tag had a body condition that did not differ to that expected for untagged bats. This suggests that transponding bats has no significant effect on body condition, enabling new opportunities for passive monitoring and large-scale long-term longitudinal studies for these animals.