The foetal origins hypothesis postulates that shocks while in utero can have long-term detrimental effects on the health and human capital formation of children. Using data from the Young Lives project for Vietnam, we examine the effects of exposure to historically abnormal rainfall among children in utero on the cognitive development of the same children from 5 to 15Â years of age. Based on data on month and place of birth, we show that positive rainfall shocks are associated with better cognitive development in children up to 8Â years of age. The effect is more pronounced when positive shocks occur in the early stage of gestation. However, such positive effects are not sustained: the impacts of positive rainfall shocks on cognition are completely absent at 10 and 15Â years of age. We contribute to the literature by examining the importance of the timing and persistence of weather shocks during pregnancy on cognitive development by tracking the same children from in utero to school age.