Aeromancy is divination by observing atmospheric phenomena.
Ceraunoscopy (also called keraunoscopy) is divination by observing thunder and lightning. Ancient peoples believed that thunder and lightning were direct communications from the gods and goddesses, such as Thor (thunder) or Zeus (lightning). The Hindu, Etruscans, and Babylonians made extensive use of ceraunoscopy.
Tinia, the Etruscan god of lightning, was particularly associated with ceraunoscopy. Similarly, Adad, the Babylonian god of thunder, lightning, and prophecy, was particularly associated with ceraunoscopy.
François de la Tour Blanche As for thunder and lightening these are concerned with the auguries, and the aspect of the sky and of the planets belong to the science of astrology.
In the Middle Ages, Europeans believed that thunder and lightning were omens of coming war, floods, or the death of an important person.
Ceraunomancy is divination by observing lightning. Ancient Roman augurs believed that lightning bolts from the east were favorable omens, while lightning bolts from the west were bad omens. Lightning bolts from the north were the worst omens. Lightning bolts from the northwest were a sign that very bad news would arrive soon.
Brontoscopy is divination by listening to the sound of thunder. Ancient Roman augurs (priests who specialized in the interpretation of auspices, the movement of birds, or sometimes other animals) believed that thunder from the left was a lucky omen or happy ending. Thunder from the right was a bad omen. Thunder on Sunday indicated the death of aan educated or wise man, such as a judge, general, or scholar. Thunder on Monday indicated the death of a woman. Thunder on Tuesday or Thursday was a good omen, indicating plenty of grain (especially wheat, which the Romans called corn, not to be confused with maize) and sheep. Thunder on Wednesday indicated the death of a prostitue or beggar or some other more general kind of bloddshed. Thunder on Friday indicated the murder of a great man. Thunder on a Saturday indicated widespread death, especially by plague.