Ptolemy’s Tetrabiblos is not usually considered as a meteorological text. I examine the sections of the Tetrabiblos that deal with weather prediction and argue that Ptolemy considers it part of astrology. I show that the way Ptolemy categorises weather prediction differs significantly from other Greco-Roman writers, including Cicero (On Divination) and Sextus Empiricus (Against the Astrologers). I argue for these conclusions: first, that Ptolemy considers weather prediction to be part of astrology – i.e., a scientific practice which includes giving an account of the causes of phenomena with reference to the stars; to give such an account for the weather requires a practitioner to go beyond the observation and cataloguing of weather signs. Secondly, I argue that understanding weather prediction as astrology means that the distinction between horoscopic and general astrology is more fluid than is sometimes thought. Finally, I will show that Ptolemy’s views on weather prediction provide a case study for his view of astral causation.

托勒密的Tetrabiblos通常不被视为气象文本。我检查了Tetrabiblos中处理天气预报的部分，并认为托勒密认为它是占星术的一部分。我表明托勒密对天气预报进行分类的方式与其他希腊罗马作家有很大不同，包括西塞罗（论占卜）和塞克斯图斯·经验（反对占星家））。我支持这些结论：首先，托勒密认为天气预报是占星术的一部分——即，一种科学实践，包括对与星星有关的现象的原因进行解释；对天气做出这样的解释要求从业者超越对天气标志的观察和编目。其次，我认为将天气预报理解为占星术意味着占星术和一般占星术之间的区别比有时想象的更加灵活。最后，我将说明托勒密的天气预报观点为他的星体因果关系观点提供了一个案例研究。