Since the industrial revolution, the world has experienced a considerable increase in population, which has led to the acceleration of the urbanization process. This urbanization expansion has resulted in the emergence of urban microclimates and the Urban Heat Island (UHI) and Urban Pollution Island (UPI) phenomena. These phenomena represent a harmful combination for public health, reaching their highest impact in urban areas where most of the population resides. Due to differences in material characteristics and the urban grid, they are not evenly distributed across the same urban area, meaning not all people are exposed to the same intensity. Analyzing their intensity is crucial in areas with vulnerable populations, who face greater challenges in maintaining comfortable indoor conditions. This research aims to propose a replicable methodology for analyzing the intensity of UHI and UPI, focusing on areas with vulnerable populations facing greater challenges in maintaining comfortable indoor conditions. The methodology is based on a mobile transect designed using social vulnerability data and prior urban characterization. It has been applied in Valladolid (Spain), where differences in vulnerability factors have been detected throughout the city. This methodology has a potential impact on decision-making, on public health and environmental justice.