The good news: heat prevention plans like early warning systems, cooling shelters, and check-in systems are effective: a 2025 study across 14 European countries over nearly 30 years found that prevention plans cut heat-related mortality by 25%.
Antonio Gasparrini, one of the study's authors and an epidemiologist at the London School of Hygiene and Tropical Medicine, told us he was struck by how clear the result was: “There is a very strong signal of effects of such interventions. It was strong evidence.”
So what works?
While we know heat prevention plans work, we don't know which interventions work best. Gasparrini said “there wasn't strong evidence of difference in interventions,” partly because plans vary too much by country to compare.
France is a European leader in heat mortality prevention. After a catastrophic heatwave claimed almost 15,000 lives in 2003, the country established one of the world’s first comprehensive response frameworks. It includes a national alert system, where the highest tier triggers national crisis centres and requires local and regional authorities to provide cooling, access to water, and check in on vulnerable residents.
Spain, following the same deadly summer, built national action plans and tools like its Daily Mortality Monitoring system. It also implemented extensive climate shelters: free, cooled public buildings open to the public during heatwaves. Barcelona has over 500 of those spaces, reachable within a 10-minute walk for 99% of the city's residents.
While it's clear cities are investing in these measures, their specific effect on the health hazards of heat is not yet proven. “We don’t know if they’re being used,” Andreas Flouris, a researcher in environmental physiology at the University of Thessaly in Greece, told us.
Best for your buck
The biggest impact per euro spent on heat mortality prevention comes from early heat warning systems, like in France, that are tied to automatic triggers, according to Shouro Dasgupta, co-author of the study on mortality and a researcher at the Euro-Mediterranean Center on Climate Change. Once a threshold is crossed, measures like opening cooling centres, activating check-ins, and issuing health guidance kick in automatically.
According to Flouris, however, Europe struggles to agree on what that threshold should be. Temperature? Sun exposure? Indoor humidity? There are 340 indicators to choose from.
Most systems default to temperature. Flouris, who worked on HEAT-SHIELD, the EU's first research project on protecting workers from climate-driven heat stress, says wet bulb globe temperature (WBGT), which factors in humidity, solar radiation, and wind, is a far more accurate measure of how heat feels.
Measures should also target the right people: an evaluation of the Netherlands' national heatwave plan by the Dutch institute for public health and environment found the strongest risk reductions among older people, as well as strong gains for women and groups of low-socioeconomic status.
Not for everyone
“Most heat health action plans are designed to reach as many people as possible,” not the people most at risk, Dasgupta said. Though heat prevention would ideally protect the most vulnerable, “climate change induced hazards, including heat waves, are widening existing inequalities, and heat health action plans need to be redesigned so that they can reach vulnerable populations more widely.”
These include the elderly, people with pre-existing health issues, and those who can't afford cooling systems at home. Paris already runs an opt-in heatwave registry for vulnerable and elderly residents, while Denmark relies on volunteers checking on neighbours.
For workers, another vulnerable group that is easy to miss, general heat advice – staying indoors, changing clothing, slowing down – simply doesn't apply, Flouris said. “The advice that you should give and the actions that you should take are very different for working people.”
He hopes the argument that heat makes workers less productive will convince employers to take heat-health seriously. His research found productivity losses of roughly 2.6% for every degree Celsius above 24°C WBGT – meaning a 15% productivity loss at 30°C WBGT. His recommended fixes cost almost nothing: “If I had to choose three, I would say water, rest, shade.”
Beyond the weather station
Ronita Bardhan, professor of sustainable built environment and health at the University of Cambridge, raises a major factor missing from this picture: not everyone experiences heat the same way – how you live dictates how strongly you're affected by it. “People experience heatwaves through their homes, through their workplaces.” These, she argues, can be retrofitted to adapt to high heat.
Generally, heat action plans only kick in once a hazard has already started, asking people “to change their behaviour for a short duration while the hazard exists, and then people may go back to their normal behaviour.”
Instead, she argues for structural interventions that “produce an environment that reduces the exposure to the heat” without requiring people to change how they live. “We have the power and the agency to do it.”