Some European cities are struggling with low tree cover, which is increasing the risk of heat-related health issues for their residents. This summer, extreme heatwaves caused the deaths of tens of thousands in major European cities, as temperatures reached record highs. In London, emergency rooms were overwhelmed with elderly patients suffering from heat-related illnesses after fainting. Dry conditions also led to subsidence, causing cracks in homes. In Paris, temperatures exceeded 40°C in late June, making daily life challenging for residents. Meanwhile, in Madrid, heatwaves caused fires to break out across the city’s outskirts. Thami conducted research on the effects of extreme heat on European cities this summer, focusing on how many buildings have adequate shade from trees. The findings were alarming: in London, Paris, and Madrid, over 90% of buildings lacked sufficient shade to counteract the urban heat island effect. Even cities considered better performers, such as Hamburg (56% unprotected) and Barcelona (70% unprotected), had significant portions of their populations without adequate heat protection. This aligns with previous studies showing that cities worldwide, including in Europe, often fail to achieve enough tree canopies to provide effective shade near homes and workplaces. Experts suggest that homes should have a view of at least three trees and be within 300 meters of a park to be adequately protected from heat. During summer 2026, many days in cities remained dangerously hot even in the evening, due to the urban heat island effect. This phenomenon occurs when cities lack sufficient shade, as tree removal, sparse planting, and poor tree health reduce natural cooling. In addition, materials like asphalt, clay, and concrete—common in urban environments—absorb and retain heat. Unshaded asphalt can reach over 70°C during heatwaves. After sunset, these materials continue to radiate heat, keeping cities warm long after the sun has set. This effect can raise ambient temperatures significantly, turning a 35°C day into a potentially life-threatening 40°C day in areas with high asphalt coverage and low shade. Tree shading is a proven solution to combat urban heat, offering both cooling and health benefits. Trees block direct sunlight from reaching heat-absorbing surfaces like asphalt and also shield people from the sun. Research has shown that tree shade can reduce the heat experienced by pedestrians by up to 18°C. Healthy trees also release water vapor through their leaves, which helps cool the air through evaporation. This natural cooling effect, combined with shading, can significantly lower temperatures, even during heatwaves, as long as trees have access to water. To effectively combat urban heat, cities need to plant more trees in areas close to homes and workplaces. A study by the Create Streets Foundation found that during a heatwave, an exposed paved area in London reached 55°C, while a shaded area just meters away was 25-30°C cooler. While cities like London have millions of trees, their effectiveness in reducing heat is limited if they are not near residential areas. Research shows that a tree canopy cover of at least 30-40% within 60 meters of homes and workplaces is necessary for significant cooling. As temperatures rise, it will be crucial to plant tree species that can withstand increasingly hot conditions. Even a small increase in temperature can significantly raise the risk of heat-related illnesses. In areas where heat islands raise temperatures from 33°C to 37°C or 35°C to 41°C, there is a noticeable increase in hospital admissions for heat-related conditions. When temperatures exceed 35°C, the human body struggles to manage the heat, leading to cardiovascular strain, dehydration, and potential heatstroke. High temperatures also affect sleep and recovery. The body typically cools down during the night to prepare for the next day. If nighttime temperatures remain above 24°C, this recovery process is hindered, leading to poor sleep quality and reduced cognitive and physical performance. Prolonged exposure to high heat can lead to a cumulative deficit, making it harder to cope with subsequent hot days. Cities like Medellin in Colombia have demonstrated the benefits of increasing urban greenery. By planting millions of plants and over 12,500 trees, Medellin saw temperature drops of up to 4.5°C in some areas and 2°C citywide. In Europe, both London and Paris are beginning to take action. London’s Heat Ready plan emphasizes urban greening, while Paris is expanding its green spaces, including through its school streets program, which creates car-free zones near schools and adds more trees. As Europe faces more hot summers, prioritizing tree planting near homes will be essential to help residents stay safe and healthy.