What is "aeromancy"

Aeromancy \A"["e]r*o*man`cy\, n. [A["e]ro- + -mancy: cf. F. a['e]romancie.] Divination from the state of the air or from atmospheric substances; also, forecasting changes in the weather.

n. Divination by use of atmospheric conditions.

Aeromancy (from Greek ἀήρ aḗr, "air", and manteia, "divination") is divination conducted by interpreting atmospheric conditions. Alternate spellings include arologie, aeriology and aërology.