The United Kingdom experienced its second significant heatwave in two months last week, exposing the country's vulnerability to extreme temperatures, particularly in urban areas. The intense heat led to disruptions such as the failure of MRI health scanners and the closure of hundreds of schools and nurseries due to inadequate cooling systems. A hosepipe ban was also implemented in Kent as water supplies came under strain.

Cities face heightened risks from extreme heat because of the “urban heat island effect,” a phenomenon where densely built environments trap and amplify heat, causing temperatures to feel several degrees higher than official readings. London’s experience exemplifies this challenge, prompting local authorities to develop strategies aimed at managing rising temperatures.

On Thursday, the Greater London Authority unveiled the “Heat Ready London” report, introduced by Mayor Sir Sadiq Khan. The plan outlines measures to safeguard the capital against increasingly frequent and severe heatwaves, aiming to provide cooling solutions in up to one million homes. Key components include installing shutters, enhancing insulation, improving ventilation, and expanding air-conditioning systems.

Industry experts stress the importance of preventing heat ingress through windows. Chris Hocknell, director of Eight Versa—a consultancy assisting building companies in climate-proofing projects—highlighted that direct solar radiation significantly contributes to indoor heat, often more so than air temperature itself. He noted that practices common in Southern Europe, such as the use of shutters and specialized glazing, will likely become standard in UK urban housing. Upgrades may include the replacement of timber-framed windows with more thermally efficient uPVC alternatives featuring double or triple glazing, and the use of special glass designed to reflect solar energy.

Additional architectural adaptations are being considered. John Stubbs, founder of sustainable paint company YesColours, pointed to the benefits of lighter roof colours, which can reflect up to 80 percent of sunlight compared to darker roofs that absorb heat. Such measures could reduce indoor temperatures by between 1°C and 5°C, with particular benefits for top-floor rooms that tend to experience the highest heat levels.

Green infrastructure is also a cornerstone of the Heat Ready plan. Expanding and managing tree cover, along with integrating greenery around buildings, aims to mitigate urban heat. A notable example is a “living wall” of plants on Regent Street, where temperatures measured near the vegetation were recorded at 20°C cooler than the adjacent street surface. This success is likely to encourage the broader installation of similar features across cities.

Complementing these initiatives, a network of “cool spaces” with air conditioning—designed to offer relief to residents unable to adequately cool their homes—is operational in London and set to expand in other urban areas. Emma Howard Boyd, chair of the independent National Heat Risk Commission, emphasized the importance of providing safe environments where vulnerable populations can escape extreme heat.

The recent heatwave set a new record for June temperatures in the UK, surpassing the previous high from 1976 by over 1°C—a substantial increase given that historical records have typically been eclipsed by only marginal amounts. The Met Office noted that temperatures began to decline toward the end of the week, with highs dropping to the mid-20s Celsius in eastern coastal areas and cooler conditions expected to follow as fresh air flowed in.