This article analyses the development of the lay observation of the weather, in the nineteenth-century France. In the 1840’s, meteorological observation becomes popular among the French middle-class. Lawyers, employees, rentiers note the indications of their instruments several times per day. They cooperate in order to publish their data and they create a learned society, the French Meteorological Society, in 1852. Their observational culture is structured by a certain kind of moral, political and epistemological values that this article puts under scrutiny.