Following the “fetal origins of adult disease” hypothesis, environmental determinants of birth weight regained interest. The authors applied a detailed spatial-time exposure model for climatological factors thought to affect fetal growth: seasonality, temperature, and sunshine. Daily climatological data (29 stations) were linked to 1,460,401 term births with an individual exposure matrix for each pregnancy. Linear regression was utilized to determine effects of climatological factors on individual birth weight and existing spatial variations in birth weight. In the Netherlands substantial regional climatological differences exist. Summer was associated with significantly reduced birth weight (16–19 g). Minimum and maximum temperatures were significantly associated with increased and reduced birth weight, respectively. Spatial birth weight differences ranged from -11 to +25 g, with lowest birth weights in inland areas. The authors demonstrate birth weight to be associated with climatological factors; negative birth weight effects of maximum temperature exposure confirm results from animal studies. Consequently, a climate footprint is visible in the spatial birth weight differences.