Recently a number of studies have been published that relate birth month to lifetime disease incidence. Each of these studies investigated a single disease. Our hypothesis-free approach systematically investigates associations between birth month and all diseases recorded in the Electronic Health Records at Columbia University Medical Center. The utility of our approach is demonstrated by confirming known disease-birth month associations, and revealing associations that bolster existing hypotheses. For example, a link between cardiovascular diseases and birth month points to seasonal risk factors associated with fetal cardiac development. Looking across all diseases revealed that patients born in late fall (October-November) have the greatest incidence of diseases that have birth month dependencies, while those born in early summer (May-July) have the least.