Chapter 7 considers astrometeorology as an established branch of knowledge, within the context of fourteenth-century developments in astronomy and technology. Mechanical clocks were prominent products of these advances, as were more accurate astrolabes and planetary tables. Most successful of the latter were the Alfonsine Tables, used by the authors of new and more ambitious treatises of astrometeorology, such as Firminus de Bellavalle. The chapter analyses the new approaches taken by inventors like Richard of Wallingford and scholars like John of Eschenden, and traces the growing prominence of Merton College, Oxford, in this field. Eschenden’s fame as a forecaster was boosted by his claim to have predicted the great plague of 1348. Related to this is the survival of his weather forecasts for 1348 to 1374. The chapter considers the rise of weather observation, and the survival of records from Lincolnshire, Oxford, Wurzburg and Basel, as evidence of a drive to give astrometeorology an empirical backing. It concludes that astrometeorology grew as an area of expert practice, despite the attacks that critics such as Nicole Oresme made against the reliability of all forms of astrology.