Spain has emerged as one of the European regions most severely affected by intensifying heat extremes, and Seville—located in the Guadalquivir Valley, one of the hottest urban corridors on the continent—sits at the sharp end of this trend. Yet, despite the severity of its thermal conditions, the city has historically lacked the kind of granular, urban-scale vulnerability analysis needed to target adaptation resources where they matter most. The research team, led by Julia Díaz-Borrego together with Alicia Alonso and Rocío Escandón, set out to close that gap by treating heat vulnerability not as a single environmental measurement but as the product of multiple overlapping factors spanning climate, buildings, and human demographics.

Technically, the framework begins with climate data drawn from the European Climate Assessment and Dataset project, using daily maximum temperatures recorded at the Seville airport meteorological station between 2008 and 2017. Following the criteria of the Spanish State Meteorological Agency, the researchers defined a heat wave as an episode lasting at least three consecutive days in which at least ten percent of monitoring stations record maximum temperatures above the 95th percentile of the July and August series from 1971 to 2000. From the decade of observations, three particularly severe events stood out: the August 2012 heat wave, the June 2017 event, and another episode in August 2017. These three served as the critical case studies for understanding how the city behaves at the extremes of its thermal range.

For each of these events, the team examined two linked indicators: the urban heat island effect, which describes how urban areas retain and generate more heat than surrounding rural land, and a metric known as the hot night excess, which captures how much nighttime temperatures exceed normal thresholds. The nighttime focus is deliberate and scientifically important. A growing body of epidemiological research, including studies on mortality across Southern Europe, has shown that hot nights are strongly associated with excess deaths, because they deny the human body the chance to recover from daytime heat stress. Nocturnal conditions, rather than daytime maxima alone, are increasingly recognized as the decisive variable in heat-related health outcomes.

The spatial analysis revealed a consistent pattern: the eastern third of Seville repeatedly registered the highest levels of thermal stress during all three heat waves, a result the researchers attribute to a combination of atmospheric and geographic factors specific to the city’s layout. During the August 2012 event, the hot night excess index tracked a marked intensification of the urban heat island within the consolidated urban fabric compared with rural surroundings. In June 2017, the correlation between the two indicators weakened, yet temperatures still rose considerably and the urban heat island intensified within city limits, with the eastern districts again most affected. The August 2017 episode showed fluctuating island patterns, but geography continued to concentrate the worst conditions in the same eastern zone.

What elevates the study beyond conventional heat mapping is its integration of microclimate simulation with socioeconomic and building-level data. Rather than relying solely on satellite-derived land surface temperatures, which often struggle to capture nighttime urban dynamics, the researchers incorporated high-resolution nocturnal microclimatic simulations capable of resolving street-level thermal behavior. Onto this thermal layer they overlaid building-scale cadastral information and census data measuring energy poverty—a concept describing households unable to afford adequate cooling or heating—and broader sociodemographic characteristics such as income, age structure, and housing conditions. The result is a multidimensional vulnerability index whose geography can be inspected at the scale of individual blocks.

The central finding is striking in its simplicity: thermal exposure and vulnerability are not the same thing. Although high temperatures were widely distributed across Seville’s consolidated urban areas, the researchers found that vulnerability was far from homogeneous, because socioeconomic and demographic conditions play a decisive role in differentiating levels of risk. Districts with nearly identical thermal profiles exhibited significantly different vulnerability outcomes depending on residents’ income, the age composition of the population, and the physical quality of the housing stock. Older residents living in poorly insulated, energy-inefficient dwellings in low-income neighborhoods face compounding risks that wealthier districts exposed to the same temperatures simply do not experience, particularly when air conditioning is unaffordable to run.

Just as important as the index itself is the framework’s insistence on visual, cartographic communication. The authors place particular emphasis on the graphical representation of results, producing clear and accessible maps that reveal spatial patterns and pinpoint critical hotspots within the urban fabric. This is not a cosmetic choice. Complex multilayered analyses of climate and social data frequently remain locked in technical reports that municipal decision-makers cannot easily interpret. By translating the framework’s outputs into intuitive visual spatial analysis, the researchers demonstrate a practical route for communicating vulnerability patterns to planners, public health officials, and elected representatives who must ultimately decide where scarce adaptation funds are spent.

The implications reach well beyond Seville. Southern European cities are warming rapidly, and projections of heat-attributable mortality in Spain through mid-century and beyond suggest a growing public health burden unless cities adapt. Frameworks like this one provide the evidence base for prioritizing interventions—whether tree canopy expansion, reflective roofing, retrofitting social housing, or targeted cooling-center placement—in the neighborhoods where they will save the most lives. By proving that similar thermal exposure can mask dramatically different vulnerability profiles, the study delivers a clear message to urban governments across the Mediterranean: climate resilience strategies that ignore socioeconomic reality will protect the wrong places. Equitable, data-driven targeting, the researchers argue, is the only path to climate-resilient cities that protect all of their residents, not merely the most fortunate ones.

Subject of Research: Mapping urban vulnerability to extreme heat in Seville by integrating microclimate simulation, cadastral data, and socioeconomic indicators.

Article Title: A decision-making framework for mapping urban vulnerability to extreme heat: a case study in a Mediterranean context

Article References: Díaz-Borrego, J., Alonso, A., & Escandón, R. (2026). A decision-making framework for mapping urban vulnerability to extreme heat: a case study in a Mediterranean context. Regional Environmental Change, 26(4), Article 189. https://doi.org/10.1007/s10113-026-02685-w

Image Credits: AI Generated

DOI: 10.1007/s10113-026-02685-w

Keywords: urban heat island, extreme heat, Seville, heat vulnerability, energy poverty, Mediterranean climate, nocturnal microclimate, urban planning, climate adaptation, social inequality, hot nights, spatial analysis