International audienceThis study is based on original observation diaries and examines why and how meteorological observations were set up within an observatory in the modern era by looking at the case of the Paris Observatory in its first decades of operation. It demonstrates the existence of multiple causes for such observations, examines practices, takes stock of instruments and raises the question of whether meteorology belonged to the observatory sciences at that time. These causes are specific to the history of the institution itself, are the result of requests from the authorities, and are part of the scientific research of the time, both physical and astronomical. In meteorology, the observatory appeared to be a place where standard...