Extreme weather variations, chronic food insecurity, and lack of coping mechanisms place children in South Asia at a high risk. While there is a large body of literature documenting the effect of precipitation extremes on child health in this region, there is a lack of research work focusing on temperature- related extremities and analyzing differential vulnerabilities among various socio-demographic groups. This study examines the effect of climate variability on birth and early childhood health parameters by combining high-resolution climate data with child anthropometry and demographic data from four South Asian countries (India, Pakistan, Bangladesh, and Nepal). We find temperature and precipitation anomalies to be strong negative predictors of child health outcomes with their effects concentrated mostly in-utero period. We further expand on our findings by looking at how these effects differ across groups based on economic, gender and social vulnerabilities.