Climate change is leading to significant warming, with elevated temperatures in urban areas compared to rural ones, negatively impacting the well-being and health of citizens. Recent research on historical heritage is shifting focus from buildings to open and transitional spaces, such as cloisters and courtyards. However, urban cloisters’ study in Italy is overlooked compared to the extensive research on open and transitional spaces in Spain and North Africa, where their role in microclimatic mitigation is acknowledged. This study aims to explore the potential for conservation and reuse of Italian urban cloisters as transitional spaces, analyzing their thermal resilience in the context of increasing climatic challenges. Through a comparative evaluation of 110 cloisters, with a focus on three case studies, the monastery of San Domenico in Vicenza, the monastic complex of Sant’Orsola in Florence, and the complex of Sant’Andrea delle Dame in Naples, microclimatic simulation models were conducted using ENVI-met software to recreate current climatic conditions and future projections. The results demonstrate how targeted interventions can enhance the thermal comfort of these historic spaces, reducing internal temperatures and positively impacting the surrounding urban environment. The research emphasizes the importance of a design approach that values the historical and architectural characteristics of cloisters, proposing solutions for sustainable reuse and an enhanced quality of life in urban environments.