The objective of the paper is to provide recommendations on the temporal and spatial resolution of rainfall measurements required for urban hydrological applications, based on quantitative investigations of the space-time scales of urban catchments and rainfall. First the temporal rainfall–runoff dynamics is studied using lag time values derived from rainfall and discharge time series for a set of urban catchments. Then the temporal and spatial structure of rainfall is analysed with high resolution rain gauge and radar measurements from the HYDROMET Integrated Radar Experiment '98 experiment for three typical intense Mediterranean rain events. In particular the evolution of the structure of the rainfall field at different time steps is investigated using geostatistics. Finally the required space-time resolution of rainfall for Mediterranean regions is estimated as a function of the surface of the catchments. According to the results, hydrological applications for urban catchments of the order of 1000 ha require a temporal resolution of about 5 min and a spatial resolution of about 3 km. For urban catchments of the order of 100 ha, it becomes a resolution of about 3 min and 2 km, that common operational networks or radars cannot provide. These results complement the scarce recommendations on resolution of rainfall for urban hydrology reported in the literature