During the last decade, there has been an increased interest on cloud computing and especially on the adoption of public cloud services. The process of developing cloud-based public services or migrating existing ones to the Cloud is considered to be of particular interest—as it may require the selection of the most suitable applications as well as their transformation to fit in the new cloud environment. This paper aims at presenting the main findings of a migration process regarding smart city applications to a cloud infrastructure. First, it summarises the methodology along with the main steps followed by the cities of Agueda (Portugal), Thessaloniki (Greece) and Valladolid (Spain) in order to implement this migration process within the framework of the STORM CLOUDS project. Furthermore, it illustrates some crucial results regarding monitoring and validation aspects during the empirical application that was conducted via these pilots. These findings should be received as a helpful experience for future efforts designed by cities or other organisations that are willing to move their applications to the Cloud.