Summer could essentially never end, with heat stress for nearly half the year.
A team of researchers at the Universitat Politècnica de València has issued a sobering cartography of the city's thermal future: without decisive action on emissions, Valencia may cease to have seasons in any meaningful sense, enduring what amounts to a permanent summer by 2100. The study, rooted in decades of observed data and three projected climate scenarios, reminds us that heat is not merely a matter of discomfort but of survival — and that the most vulnerable among us will bear the heaviest burden of a crisis they did little to create. What was once the rhythm of Mediterranean life, the reliable turning of warm and cool, is being quietly unmade.
- Heat waves in Valencia have already nearly tripled in duration since 1979, signaling that the transformation of the city's climate is not a future threat but a present reality.
- Under the worst-case emissions scenario, up to 300 days per year could exceed a heat index of 50°C — a figure that strains the imagination and the body's capacity to cope.
- Humidity compounds the danger in ways raw temperature cannot capture, stripping the body of its ability to cool itself and turning prolonged heat events into cascading public health emergencies.
- Elderly residents, children, and those with existing illnesses stand at the sharpest edge of this risk, with heat-related mortality expected to surge if urban systems remain unprepared.
- Researchers are pressing cities to act now — green corridors, cool roofs, climate refuges, and early warning systems are proposed not as luxuries but as essential infrastructure for a livable future.
- The study is embedded in a broader European research initiative, underscoring that Valencia's predicament is a Mediterranean-wide reckoning, not an isolated local forecast.
Researchers at the Universitat Politècnica de València have published a stark projection in the journal Urban Climate: if greenhouse gas emissions continue unchecked, Valencia could experience a near-permanent warm season by the end of this century, with heat waves so frequent and prolonged that the city's residents may spend the better part of each year under dangerous thermal conditions.
The data already tells a troubling story. Since 1979, Valencia has recorded two additional heat wave episodes per decade, and the average duration of those events has grown from under ten days to nearly twenty-five. Lead researcher Ana Fernández-Garza and her team go further, incorporating the heat index — a measure that combines temperature and humidity to reflect actual physiological stress — rather than relying on temperature alone. As humidity rises alongside heat, the body's ability to cool itself through perspiration breaks down, transforming manageable warmth into genuine medical crisis.
The study maps three futures. Even in the most optimistic scenario, with deep emissions cuts, heat waves would still double in frequency and peak above 40°C. A middle path of partial mitigation projects six to eight heat waves per summer, some exceeding a month in duration. The worst case — business as usual — renders April through November a near-unbroken thermal season, with heat stress indices surpassing 50°C for roughly 300 days a year.
Urban planning researcher Eric Gielen warns that without intervention, summer may simply never end. The human cost falls hardest on the elderly, young children, and those with chronic illness, populations least equipped to absorb the compounding effects of heat and humidity. The research team responds to their own diagnosis with a set of concrete prescriptions: expand urban greenery, install reflective roofing, establish public climate refuges, and build early warning systems linked to health protocols — with explicit priority given to poorer neighborhoods that lack shade and have older housing.
The study forms part of The HUT, a Horizon Europe-funded initiative, a reminder that Valencia's predicament is shared across the Mediterranean and that the window for meaningful adaptation is narrowing.
A research team at the Universitat Politècnica de València has mapped out a troubling future for the city: by the end of this century, summer could stretch across half the year, with heat waves becoming so frequent and intense that residents may spend months at a time under dangerous thermal conditions.
The study, published in the journal Urban Climate, documents how heat waves have already intensified over recent decades. Since 1979, the city has experienced two additional heat wave episodes per decade. More striking still, the average duration of these events has nearly tripled—from less than ten days to almost twenty-five. But the researchers' projections for the coming decades paint a far more severe picture.
Ana Fernández-Garza, the lead researcher at the Institute of Water and Environmental Engineering, explains the stakes plainly: if greenhouse gas emissions continue at their current pace, Valencia could face a thermal season that lasts nearly unbroken from spring through fall. The city might endure six consecutive months of elevated heat risk, with temperatures potentially exceeding fifty degrees Celsius. The research incorporates a crucial variable that standard temperature readings miss—the heat index, which combines temperature and humidity to measure the actual physiological stress on the human body. This matters enormously. As humidity climbs alongside temperature, the body's ability to cool itself through perspiration diminishes, turning what might seem like a manageable heat into a genuine health crisis.
The study examines three possible futures. In the most optimistic scenario, assuming dramatic cuts to greenhouse gas emissions, Valencia would still see its heat waves double in frequency, with peak temperatures surpassing forty degrees and individual episodes lasting around fifteen days. The middle scenario, with partial climate mitigation efforts, projects six to eight heat waves per summer, some lasting more than a month, with heat index values climbing to forty-five degrees. The worst case—continuing current emission trends—sketches a landscape almost unrecognizable to anyone living in Valencia today. From April through November, the city would experience what amounts to a permanent warm season, punctuated by extreme heat waves that could last weeks at a time, with thermal stress indices exceeding fifty degrees for roughly three hundred days each year.
Eric Gielen, an urban planning researcher on the team, underscores the cumulative danger: "The number, duration, and intensity of heat waves are rising continuously. Without action, we could reach a point where summer essentially never ends." The implications for public health are severe. Elderly residents, young children, and people with existing health conditions face the greatest risk from prolonged heat exposure and the compounding effect of humidity. Heat-related illness and mortality would likely surge.
The research team—which includes Fernández-Garza, Gielen, Manuel Pulido-Velázquez, Dariana Ávila-Velásquez, Adrià Rubio-Martín, and Héctor Macián-Sorribes—has moved beyond diagnosis to propose concrete adaptations. They recommend expanding green spaces and vegetation throughout the city, installing cool roofs and reflective materials on buildings, establishing climate refuges where residents can escape extreme heat, and creating early warning systems tied to public health protocols. These measures, they argue, must be woven into urban planning with explicit attention to equity—ensuring that the poorest neighborhoods, which often have fewer trees and older housing stock, receive priority investment.
Gielen concludes with an observation that cuts through the academic language: climate change is not a distant threat. It is already reshaping cities. Valencia, like other Mediterranean urban centers, must begin now to build the infrastructure and systems that will allow people to live safely alongside heat that would have been unthinkable a generation ago. The study is part of a larger European research initiative called The HUT, funded through the Horizon Europe program, suggesting that this problem extends far beyond one Spanish city.
Notable Quotes
If urgent mitigation measures are not taken, the city could experience six consecutive months of elevated thermal risk with temperatures exceeding 50°C.— Ana Fernández-Garza, lead researcher, UPV Institute of Water and Environmental Engineering
Climate change is not a future phenomenon—it is already affecting our cities. Valencia must prepare to coexist with extreme heat in a safe and resilient way.— Eric Gielen, urban planning researcher, UPV
The Hearth Conversation Another angle on the story
When you say heat waves have nearly tripled in duration since 1979, what does that actually feel like for someone living through it?
It's the difference between a crisis you can endure and a condition you have to survive. A ten-day heat wave, you stay inside, you manage. Twenty-five days, and you're talking about people who can't afford air conditioning running out of money, or elderly people whose bodies simply can't regulate anymore. The danger compounds.
The study mentions humidity as a multiplier. Why does that matter more than just temperature?
Because your body cools itself by sweating and evaporation. When humidity is high, that mechanism fails. You can be at forty degrees with low humidity and survive it. At forty degrees with eighty percent humidity, your body is essentially trapped—it can't shed heat. That's when heat stroke becomes real.
Three hundred days of extreme heat annually—is that even survivable for a city?
Not as we currently live. You'd need to fundamentally redesign how people work, move, and rest. Outdoor labor becomes impossible during peak hours. Power grids strain from air conditioning demand. Hospitals overflow. It's not just uncomfortable; it's a reorganization of urban life.
The researchers propose green spaces and cool roofs. Can those actually make a difference at that scale?
They help, but they're not a solution alone. A green roof cools one building. You need thousands of them, plus urban forests, plus changes to how we generate and use energy. It's necessary but not sufficient without also cutting emissions.
Who gets hurt first if these projections come true?
The people who already have the least—elderly on fixed incomes without air conditioning, children in poorly ventilated schools, outdoor workers with no choice but to labor in heat. Inequality becomes a heat vulnerability map.