Cities in southern Europe are particularly affected, researchers found in the 2026 Europe Cities Report published in The Lancet on Thursday.
Southern European cities recorded 132 additional heat-related deaths per one million inhabitants between 2015 and 2024 - an increase of 161 per cent compared to the period between 1991 and 2000.
Cities in western Europe, by comparison, recorded an additional 64 heat-related deaths on average in the same period, below the continent-wide average increase of 82.
"Cities have a central role in addressing climate change by implementing adaptation and mitigation solutions that deliver resilient and low-carbon communities, boost local economies, and improve citizens' health," the team writes.
At the same time, cities are increasingly feeling the effects of climate change, as "Europe is facing more rapid warming than other world regions, and record-breaking summer temperatures."
Residents are also increasingly exposed to toxic smoke from wildfires, the study found, with the number of exposure days rising by 7 per cent between 2003 and 2023 across Europe. Cities in southern and eastern Europe were found to be particularly affected.
Global warming is fuelling a rise in infectious diseases in European cities that had previously been considered tropical diseases, including dengue, Zika and chikungunya, as the mosquitoes that transmit the viruses are becoming increasingly established in Europe, according to the study.
The risk of contracting dengue fever rose by 111 per cent on average across European cities between 2015 and 2024, compared to the period from 1981 to 2010, with eastern European cities seeing the highest increase of 369 per cent. The researchers observed similar trends for Zika and chikungunya.
Cities across Europe are also affected by rising concentrations of pollen, according to the researchers, who examined climate change-related effects on health in over 800 European cities.
Birch pollen intensity increased on average in eastern European cities, with an average rise of 137 per cent recorded in Budapest between 2015 and 2024. Similar trends were observed in southern Europe regarding olive pollen concentration.
"Compared with 1991-2000, total seasonal birch concentrations increased in western European cities, including a 66 per cent rise in Berlin, Germany and 82 per cent in Brussels, Belgium," the study said.
However, the researchers noted trees are also an important means of mitigating the effects of climate change.
"Urban trees, one of the high-density elements of green spaces in cities, provide essential ecosystem functions that directly benefit health by reducing heat stress, improving air quality, and supporting mental wellbeing," they said.
The UN Economic Commission for Europe recommends a minimum threshold of 30 per cent for minimum canopy cover, the researchers noted, adding that only 14 per cent of European cities meet this target.
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