This study addresses the impact of urbanization and Urban Heat Island (UHI) on long-term climatic and hydrologic variables, particularly cloud coverage and precipitation. Urban landscapes modify the boundary layer because of differences in heat capacity and albedo of urban materials. UHI-thermal perturbation of the boundary layer and enhanced convergence resulting from an increased surface roughness may affect clouds and precipitation. Previous works show contrary impacts especially on precipitation over urbanized areas. Using a statistical approach, the relationship between the changed landscape from 1981 to the present, and to less urbanized nearby locations will be assessed for the properties which influence their energy budget, and its relationship to cloudiness and precipitation over and downwind of those areas. A ‘UHI signature' should be detected over time, defined as the difference in air temperature between urbanized and less developed outlying areas, and should match with changes in land cover. Remote sensing observation from satellites and radar, together with ground station datasets, deliver consistent long-term information over time and space of air and land variables.