Image via Wiki Commons.

Barcelona may be one of the most attractive cities in the world, but when the heat really gets going, it can become unbearable.

It slips through old windows and into apartment blocks; it rises from asphalt and stone after sunset. It’s everywhere. In the city’s tight, crowded streets, many homes still lack air conditioning. For residents who are elderly, isolated, chronically ill, or living in poorly ventilated apartments, heat goes from uncomfortable to outright dangerous.

When heat becomes a public-health threat, people need nearby places to cool down, rest, and drink water. The solutions can sound deceptively simple: plant more trees, create more shade, and tell people to hydrate.

But can people actually reach that shade? Is there a cool place near their home? Near their workplace? Is it open when they need it? Can they enter without buying anything?

These are not simple questions to answer. They’re tricky urban-design challenges that weave in the environment, public-health, and inequality all at once.

Barcelona is trying to answer them with refugis climàtics — climate shelters. These are parks, libraries, museums, civic centers, sports facilities, and rewilded schoolyards where people can cool down for free. Some are indoors and air-conditioned. Others are outdoor spaces with shade, water, and vegetation.

The idea is simple: in a hotter city, cooling should be treated as public infrastructure.

The Hot Elephant in the Room

The world has seemingly resigned itself to face the brutal consequences of climate heating head on. But accepting or ignoring it won’t make it any easier.

The Mediterranean is one of the regions most exposed to rising temperatures. Cities are especially vulnerable because asphalt, concrete, and stone absorb heat during the day and release it slowly after sunset. This urban heat island effect can keep streets and apartments dangerously hot long after the sun goes down.

Across Europe, extreme heat has become the deadliest environmental hazard. In 2023, the continent recorded an estimated 47,690 heat-related deaths, with researchers warning that the true number may have been closer to 58,000 because of limitations in counting methods. Southern Europe carried much of the burden: Spain saw 175 deaths per million people, while Greece reached 393 per million.

Then came Spain’s historic summer of 2025, the warmest on record in the country. The Spanish meteorological agency AEMET reported that the summer was 2.1°C above the 1991–2020 average and surpassed the previous record set in 2022.

Researchers later estimated that Spain saw 15,711 heat-related deaths that summer. Strikingly, 10,831 of those deaths were associated not with spectacular one-day temperature spikes, but with prolonged exposure to moderately high temperatures. In other words, the killer wasn’t always the dramatic heatwave. Often, it was the slow accumulation of physiological stress over hot days and hot nights.

This is what Barcelona is trying to fight.

The first step is admitting the problem. The second step is having the data.

From Pilot to Large-Scale Project See the interactive map here.

Heat doesn’t affect everyone equally.

Heat-related mortality is generally higher among older people, especially those over 80. Women often face higher heat-related mortality than men. Poverty, social isolation, chronic illness, and poorly insulated housing all sharpen the risk.

So, if you want to create true climate shelters that can save lives, that’s what you need to think about.

But climate shelters can’t succeed as a glorified map of air-conditioned rooms. You need to ensure that the spaces are available when people need them and that they help people who need them most.

In an April 2026 comment in Nature Climate Change, a multidisciplinary team proposed a broader framework built on three pillars: local climate knowledge, operational integration with public health systems, and governance models centered on equity and collaboration.

Libraries and municipal buildings are also part of the project. Image via Flickr.

Local knowledge matters because heat is intensely specific. One street corner may bake under reflected sunlight, while another is cooled by shade and wind. Outdoor shelters must be assessed through temperature, humidity, solar radiation and wind speed. Indoor shelters need evaluation of their building envelopes and passive cooling capacity.

Barcelona’s climate shelter network began as a pilot funded by the European Union. Barcelona’s Refugis Climàtics a les Escoles program targeted 11 vulnerable public schools and introduced what planners often call blue, green and grey measures: water points, vegetation, shade structures, soil, permeable surfaces and redesigned play areas. They removed 1,000 square meters of concrete and tarmac and added over 2,000 square meters of new shaded areas. They also installed 26 new public water points.

Since then, it has evolved into a permanent municipal system.

What Counts As a Climate Shelter?

Barcelona now has nearly 400 climate shelters during the summer season, according to 2025 municipal reporting. These include libraries, civic centers, sports complexes, museums, parks, historic gardens, and transformed schoolyards.

The goal is proximity. Barcelona considers a shelter useful to residents if they can reach it within a 10-minute walk. A Barcelona Supercomputing Center visualization notes that municipal data put 98% of residents within a 10-minute walk of a summer climate shelter, though researchers continue to study whether the network adequately serves the most heat-vulnerable groups.

Outdoor shelters generally need to be large enough to provide meaningful relief, while indoor shelters must offer enough space, accessibility, toilets, and drinking water. The city also designates smaller “micro-shelters” in some cases, which can be smaller.

The places keep their original use, in addition to becoming a shelter. The library is still a library, and the shopping centers are still shopping centers, they just support people to recover from heat. All have to be free (except swimming pools). Most of them have good accessibility, toilets, and drinking water. Indoor spaces receive some funding from the local municipality for this.

Some climate shelters are, in practice, existing municipal buildings with air conditioning and a new status. This status (and the fact that it is publicly advertised) is meant to encourage people to take advantage of these cooling conditions.

Trees Help But They Take Time

Barcelona’s climate shelter is complemented by other policies, like the Tree Master Plan, running from 2017 to 2037. The plain aims to increase overall tree canopy cover from a baseline of 5% to 30% of the municipal surface. It also calls for at least 40% of municipal tree species to be adapted to hotter, drier Mediterranean conditions, and for no single species to make up more than 15% of the tree population.

Image via Wiki Commons.

That biodiversity rule is more than a nice ecological gesture. It’s basically risk management.

Cities that rely too heavily on one tree species can lose large parts of their canopy to a single pest, pathogen, drought, or climate shock. A diverse urban forest is harder to wipe out. It is also more likely to survive the hotter, drier Mediterranean summers now taking shape.

That may sound provocative, but it captures a real change. Urban vegetation is no longer just decoration; it’s functional. It’s cooling infrastructure, public-health infrastructure, and climate infrastructure.

Still, trees require time. They need years to mature, and they can die if planted without enough soil, water and care. A climate shelter can open tomorrow. A canopy must be grown.

The City as Shelter Aerial view of Barcelona. Image credits: Logan Armstrong.

Ultimately, climate shelters can offer relief quickly, but they cannot, by themselves, cool a city. They are emergency infrastructure, a band-aid for the climate problem. None of these places can solve the deeper problem if homes remain dangerously hot, streets remain exposed, and public refuges close just when heat is at its worst.

Air conditioning sits uneasily at the center of this debate. During extreme heat, it saves lives. For older people, people with chronic disease, and residents in poorly ventilated apartments, mechanical cooling can be the difference between discomfort and medical crisis.

But air conditioning is not equally available, and it costs money to install and run. It can be out of reach for people living with energy poverty. It also pushes waste heat into the street and, depending on how electricity is produced, can add to the emissions that make future summers hotter.

Barcelona’s climate shelters aren’t a grand solution to climate change. They won’t make a dent in global emissions or undo decades of warming. They won’t even keep everyone safe during a heatwave.

But they do something cities urgently need to do more often. They turn climate adaptation into something visible, local, and usable.

They can be a circuit breaker, a much-needed respite from hot days and nights. They can give people a place to lower their body temperature, drink water, rest, and recover before heat stress turns into a medical emergency. For the most vulnerable residents that access can be life-saving.

For a country (and a world) suffering more and more from climate change, this approach is becoming more important than ever.