The spatial and temporal variability of rainfall at the scale of urban areas is very important and cannot be accurately captured by rain gauge networks of reasonable densities installed by local authorities. Weather radars are costly and complex devices that many cities cannot afford, and the radar measurement of rainfall is not yet fully reliable and depends on many parameters. All cities worldwide are equipped with mobile telecommunication networks. Mobile communication networks operate in wavelengths attenuated by rainfall. The measurement of this attenuation along communication links allows estimating the mean rainfall along this path. This technique has first been viewed to calibrate weather radar data. As microwave communication links are large in cities, they might constitute a self-sufficient approach for mapping of rain field in urban areas.