The Inca god associated with thunder and lightning was Illapa. He was a major weather deity whose powers also extended to rain, storms, agriculture, and warfare.
Illapa was often described as controlling the atmosphere. In one traditional explanation, he carried a sling and a club: striking a vessel produced thunder and lightning, while the water released from it became rain. This linked dramatic sky phenomena directly to divine action and the survival of crops.
His importance went beyond weather. Illapa was invoked during droughts and was connected with military protection, making him especially significant to an expanding empire whose agriculture and campaigns depended on favorable conditions. He was sometimes ranked among the most important gods of the Inca pantheon, after Viracocha and Inti.
The name appears in several forms, including Apu Illapa, Ilyapa, Chuquiylla, and Libiac. Regional Andean thunder deities were sometimes identified with or absorbed into his cult. Cuycha, by contrast, was associated with the rainbow; Viracocha was a creator deity, and Inti represented the Sun.