Understanding how weather conditions during early development influence reproductive success is essential for predicting avian responses to climate change. We used a 40-year dataset from a nest-box population of collared flycatchers (Ficedula albicollis) to examine how temperature and precipitation during the incubation and nestling periods affected three key components of reproductive performance: hatchling number, fledgling production, and local offspring recruitment. We found that higher ambient temperatures during the nestling period were associated with a decreased probability of brood failure and a higher number of recruits. In contrast, a higher sum of precipitation during the nestling stage was associated with an increased likelihood of brood failure. Interestingly, weather conditions during incubation had no statistically detectable influence on reproductive performance. Moreover, our results indicated that the within-season variation in climatic conditions, rather than the between-season variation, was primarily associated with reproductive outcomes. These findings underscore the importance of considering both overall climate conditions across seasons and short-term weather parameters within breeding seasons when evaluating reproductive success and predicting the ecological consequences of climate change.