Extreme weather events, such as heat waves, are occurring more frequently and intensively, imposing new climate-adaptation demands on municipal planning. We conducted a design study across the domains of urban planning and urban climate research, and identified challenges regarding a lack of heat-related information in current planning processes, and the high complexity of effective climate data representation. To address these challenges, and so enhance the information flow between these domains, we developed Urban Climate InteracTable, an immersive interface that supports exploratory analysis of spatio-temporal climate simulation data integrated with an urban environment representation. We describe several use cases in which this interface can be utilized to assist with planning-related decision processes and to communicate heat-related phenomena. We present the feedback obtained from our collaborating domain experts and relevant external experts, and reflect on our experiences throughout the design study. From this, we offer insights for future research.