As in other premodern societies, the economy and society of Koryŏ Korea (918–1392) were greatly affected by climatological phenomena, particularly rain and drought. However, climate played a critical role in the early formation of Koryŏ, especially in reinforcing a sociocultural belief system that supported monarchical authority. The kings utilized a “menu” of rituals designed to appease Heaven and create favorable climate conditions, which legitimated the temporal and spiritual power of the king. The different rituals can be categorized as personal rituals, private rituals, and public rituals. While climate crises threatened the economic and social stability of Koryŏ society, they were also opportunities for the Koryŏ rulers to display and reaffirm their supreme economic and juridical authority. The kings demonstrated their power by reducing corvée labor and taxes, postponing or eliminating monastery construction, and commuting judicial punishments. While weather and climate were natural phenomena, the social responses to weather were encapsulated in a ritual system that reinforced both the personal responsibility of the king and popular belief in the power and authority of the king to affect the physical and metaphysical environment.