The works of ancient Greek playwrights are getting a second act as clues for climate scientists. Few historical accounts of Mediterranean weather exist prior to the third century B.C.E. Climate researchers are particularly interested in the regular occurrence of sunny midwinter periods, called Halcyon days, during ancient times. In Greek mythology, the goddess Halcyon insulted Zeus, who in spite transformed her into a bird that can lay its eggs only during midwinter. Out of pity, Zeus provided her with 14 days of calm midwinter weather each year to lay her eggs in security. Scientists rummaged for references to Halcyon days in 43 plays performed at the outdoor Theatre of Dionysus in Athens, pictured, during the fifth and fourth centuries B.C.E. The plays included seven references to stretches of calm, sunny winter days, suggesting that Halcyon periods were common during the classical age, the researchers report this month in Weather. Scientists now know that Halcyon days are caused by stagnant high-pressure weather systems, rather than vengeful gods, enabling them to use the theatrical weather records to study how the region’s climate evolved over time.