In the developing world, weather conditions during gestation affect fetal development and birth outcomes, as well as early childhood development, largely because weather fluctuations affect food availability, and accessibility to healthcare facilities. This study estimates the effect of in-utero temperature shocks on learning outcomes in school. To this end, I exploit data on 950,000 second grade students in Peru who took the national student evaluation between 2014 and 2016, paired with data on weather conditions during gestation in their district of birth. In-utero temperature shocks reduce significantly learning outcomes in communication and mathematics. Temperature shocks increase the probability of being classified as remedial in math by 2 percentage points, and decrease the likelihood of obtaining a satisfactory grade by a similar magnitude. I find heterogeneity in these effects, with cool regions more severely affected by cold shocks, and warm regions more severely affected by hot shocks.