There exists an urgent need to assess the possible impacts of climate change on the Intensity-Duration-Frequency (IDF) relations in general and on the design storm in particular for improving the design of urban water infrastructure in the context of a changing climate. At present, the derivation of IDF relations in the context of climate change at a location of interest has been recognized as one of the most challenging tasks in current engineering practices. The main challenge is how to establish the linkages between the climate projections given by Global/Regional Climate Models at global/regional scales and the observed extreme rainfalls at a given local site or at many sites concurrently over an urban catchment area. If these linkages could be established, then the projected climate change conditions given by climate models could be used to predict the resulting changes of local extreme rainfalls and related runoff characteristics. Consequently, innovative downscaling approaches are needed in the modeling extreme rainfall (ER) processes over a wide range of temporal and spatial scales for climate change impact and adaptation studies in urban areas. Therefore, the overall objective of the present paper is to provide an overview of some recent progress and shortcomings in the modeling of extreme rainfall processes in a changing climate from both theoretical and practical viewpoints. In particular, another focus of this paper is on the recently published technical guide by the Canadian Standards Association (CSA PLUS 4013:19) entitled “Development, interpretation, and use of rainfall intensity-duration-frequency (IDF) information: Guideline for Canadian water resources practitioners” to provide some guidance to water professionals in Canada on how to consider the climate change information in the design of urban water infrastructure.