The two great bubonic plague outbreaks of history, Justinian's Plague and the Black Death were responsible for the deaths of over one hundred million individuals across Eurasia and Africa. Both occurrences of the plague coincided with climatic shiftsthat are well documented by both literary and physical evidence. This brief history explores the possibility that both Justinian's Plague and the Black Death were precipitated by climatic shifts preceding their respective eras and that these changes also contributed to disappearance of each pandemic. A scientific analysis investigating the climatic changes including the anomalous weather of 535-536 A.D., the Medieval Warm Period, and the Little Ice Age are correlated with literary evidence recording the transmission and dormancy sequence of the plague. Although distinct differences exist between the origins of climate change in the periods preceding each plague, the effects of such changes clearly resulted in conditions ideal for the resulting pandemics.