A detailed urban surface exchange parameterization, implemented in a meso-scale atmospheric model, has been used to study the urban heat island (UHI) intensity during a summer period in the city of Basel, Switzerland. In this urban parameterization, the city is represented as a combination of three urban classes (road, roof and wall), characterized by the size of the street canyon and the building and is thus able to take into account the momentum sink over the entire height of the building, as well as the shadowing and the radiation trapping effects. A control experiment including all the urban parameters describing the city centre of Basel produced a canyon air temperature that compared well with observations. A series of experiments was then conducted in which successively each of the urban parameters characterizing the city centre was changed providing the basis for an assessment of its effect on UHI mitigation.