After three years in Maths and Computer Science at the University of Brest, Sébastien Léas joined the Air Force in 1999 to become a weather forecaster. He completed his initial speciality training at the École Nationale de la Météorologie (ENM) in Toulouse (1999-2000, then 2001). In 2005, he reoriented his career by joining Météo-France. He graduated from the ENM (Class of 2005-2007) and was assigned to the Departmental Centre of Saint Quentin in the Aisne as a departmental forecaster. From 2009 to 2011, he worked at the Commercial and Communication Department of Météo-France in Paris, as a project manager for professionals and companies. Since September 2011, he has been working in the Media Unit of Météo-France as a forecaster, in charge of producing national forecast maps, writing bulletins, briefings, interviews, and presenting the video bulletins available on Array.