Basque Country researchers map heatwave vulnerability across three Spanish cities

The University of the Basque Country said on 7 October that its SAREN research group had mapped heatwave vulnerability across individual buildings and open public spaces in Bilbao, Madrid and Cáceres. The work points to substantial differences within each city, giving local planners a more detailed way to identify places that may need heat adaptation.

The researchers describe a method that combines socioeconomic conditions with the characteristics of buildings and their surroundings. Their account says vulnerability can differ even between locations in the same neighbourhood. The maps identify possible priorities; the available account does not establish that using them has reduced heat exposure or prevented illness.

How the three-city heatwave assessment works

Heatwave risk cannot be measured by temperature alone, researcher Irantzu Álvarez said in the university's announcement. The team considered how a city is built, which places face the highest temperatures, how many people are affected and how able those residents are to protect themselves. That approach distinguishes a hot place from a place where people may be especially vulnerable to the heat.

Researcher Laura Quesada said the team assessed each building and open space in Bilbao, Madrid and Cáceres, three cities in different climate zones. The work draws on multiple data sources to combine social, building and environmental variables. The resulting maps are intended to show variation at a finer scale than a single citywide figure would reveal.

The study is listed in the journal Cities under the title ‘Assessing urban heatwave vulnerability through a multiscale and multicriteria GIS-based approach: Evidence from three Spanish cities,’ with DOI 10.1016/j.cities.2026.107514. The full journal article was not accessible for this account, so details of the model's validation, uncertainty and city-by-city results cannot be independently assessed here.

Why income and age change the picture

The research group says socioeconomic variables were important in all three cities. In its assessment, lower-income people and older people were among those more vulnerable. The university's account does not give effect sizes or numerical comparisons between the cities, so the finding should not be read as a ranking of Bilbao, Madrid and Cáceres.

The team also says a household's means to protect its home can affect how the building's sensitivity to heat translates into vulnerability. That distinction helps explain why buildings with similar physical characteristics need not present the same level of risk to the people inside them. It also makes residents' circumstances relevant when cities decide where adaptation work should begin.

The broader concern is supported by the Intergovernmental Panel on Climate Change's 2022 assessment of cities and settlements. The IPCC identifies increased urban climate risks and describes how poverty and limited access to services can compound vulnerability. It also identifies heightened heat-related health risks for older people. That assessment supplies context for considering social conditions; it does not validate the new Spanish maps or their particular results.

What municipalities could do with the maps

The SAREN group says the maps could help municipalities identify buildings or types of buildings to prioritise for renovation and other adaptation measures. Mapping vulnerability at building and open-space level could direct attention to places that a broad city average might obscure. The researchers say applying the method in three cities showed it could be replicated elsewhere, but the available account does not document its validation in additional cities.

The research forms part of the OLADAPT project, which the university says is funded by Spain's Ministry of Science, Innovation and Universities. The project involves the Polytechnic University of Madrid, the University of Extremadura and the UNESCO Chair in Sustainable Development and Environmental Education at the University of the Basque Country. That collaboration places the mapping work within a wider effort to assess ways of adapting buildings and outdoor spaces to heat.

The immediate result is a way to describe where heat vulnerability may be concentrated, according to the research team's account. The sources reviewed do not establish that a city has adopted the maps, chosen renovations because of them or measured a health benefit. Those outcomes would require evidence beyond the three-city assessment described in the announcement.