Saint-Omer is a municipality of 15 000 inhabitants at the center of an urban center of 46 000 inhabitants composed by four other municipalities (Longuenesse, Arques, Saint-Martin-lez-Tatinghem et Blendecques) and at the heart of the Communauté d’Agglomération du Pays de Saint-Omer (CAPSO). It consists of a dense urban part contiguous to the Marais audomarois which is a natural and heritage area internationally recognized as world biosphere reserve by UNESCO within the Man & Biosphere-program. The Marais audomarois is also recognized as a RAMSAR site (wetland of international importance) and partly as Natura 2000 site and it hosts a biodiversity to be preserved. The city of Saint Omer also has emblematic green spaces which is a refuge for biodiversity for the city (Public garden of 20 hectares, the motte castrale and the garden of Saint-Bertin Abbey). The recent implementation of the Nature and Biodiversity Plan aims to improve the living conditions through the development of biodiversity in urban areas , in particular at the heart of the city which is characterized by its mineral aspect. In addition to its natural heritage, the city has an emblematic built heritage protected under the Site Patrimonial Remarquable-classification which includes historical monuments.

The city of Saint-Omer is involved in the Cool Towns project in order to enhance the fight against heat stress with the Urban planning and Development Agency Saint-Omer/Flandre Intérieure (AUD) which advises it about the urban planning projects and the CAPSO in charge of the urban tool Plan Local d’Urbanisme Intercommunal (Local Inter-municipal Urban Plan). In its territory, the city is responsible for road works and urban planning and wants to integrate gradually the heat stress issue into all public policies – in particular : plan for renovation of schoolyards, thermal renovation of schools, transformation of publics spaces, district developments projects – thanks to the experience of Cool Towns project and its partners.