To produce a weather forecast for soaring flight, meteorologists use, together with other data, a vertical sounding, involving (dry) temperature and wet-bulb temperature at several heights. This sampling results in a collection of data which has to be exploited. Usually the points are drawn on a preprinted paper form. In this article, we propose a method to assist the process in the production of the vertical sounding diagram. The paragraphs of the article develop the topics: Previous work, formulae, general outline of the program, analysis and design decisions, data structures, drawing the diagram, some deductions, further work, conclusions, and bibliography. Two photographs of the screen are included in the article: a general view, and the result of a zoom on the most significant part of the diagram.