1. The study of the behavior of planets in the solar system and this relationship to the weather.
2. The investigation of the (alleged) influence upon the weather, climate, etc. of planetary and stellar phenomena; such as, sun-spots, phases of the moon, comets, meteors, and planetary conjunctions.

This was a branch of an older natural astrology; and the term is often applied to a pretended prognostication of the weather, which is no better than modern "astrology".