A future increase of short-term precipitation intensities may lead to problems in sewer systems, such as increased overflow volumes and flood risks. To quantify the consequences, downscaling of climate model precipitation is required to the scales relevant in urban hydrology. In the SUDPLAN project, a system where users may upload historical time series to be used as a basis for such downscaling is being developed. In this paper, the method (Delta Change) is outlined along with brief descriptions of the technical solution and result visualization.