It is July 2036. London is in the middle of its fourth consecutive day above 40C. Before leaving for work, you automatically lower your external shutters and sling a rechargeable fan around your neck. Your phone suggests a slightly longer walking route than usual but it is almost entirely shaded. At the Tube station, you refill your water bottle before boarding an air-conditioned Piccadilly line train. At lunchtime, children splash through fountains in Paternoster Square while office workers cool off beneath newly planted plane trees. A friend texts: "Fancy a dip after work?" He is not suggesting the lido. He is talking about the wild swimming ponds at East London Waterworks Park in Waltham Forest.
The picture we paint here might sound fanciful. But when we asked the people redesigning London's future, from City Hall and the London Fire Brigade to architects, engineers and climate scientists, to imagine a 40C week 10 years from now, they described a capital that looks and lives rather differently. Streets are shadier. Homes are designed to keep heat out rather than trap it in. Water is everywhere. And Londoners themselves are beginning to adapt, changing the way they travel, work and cool off. Canadian cities facing their own rising heat risk are watching closely.
No one can say exactly what London's climate will look like in 2036, but the city is already getting a glimpse. Record-breaking June temperatures, overheated classrooms, grass fires and heat-related disruption are no longer once-in-a-generation events but increasingly familiar features of the British summer. Last month, an international conference on extreme heat, due to take place in a century-old, non-air-conditioned building at The London School of Economics and Political Science, was cancelled because of extreme heat. Climate projections suggest summers like those once considered exceptional are becoming increasingly likely as the planet warms, with heat now killing more people in England than any other weather hazard.
"The dangerous heat we've experienced is a glimpse of London's future," says Rob Anderson, research director at Centre for London. "Children are struggling to learn in overheated classrooms. Patients and NHS staff are sweltering in hospital wards. And thousands of Londoners live in dangerously hot homes." The same warnings apply across Canada, where the 2021 British Columbia heat dome killed hundreds and exposed the vulnerability of older apartment stock.
City Hall certainly thinks so. Last month it unveiled its first Heat Ready London plan, acknowledging that extreme heat is no longer an occasional inconvenience but one of the capital's defining climate risks. But what does a genuinely heat-ready London actually look like?
Buildings that breathe
London's love affair with glass may soon look outdated. In a city currently designed to capture precious winter sunshine, tomorrow's homes will instead be built to keep summer heat outside. That is a problem for many of today's developments, says Dr Giorgos Petrou, senior research fellow in building physics modelling at University College London. High-rise apartment blocks with large south-facing windows, limited ventilation and sealed facades can quickly become uncomfortably hot, trapping heat with nowhere for it to escape. The same is true of one of London's favourite home improvements: loft conversions with large roof lights. "Those are two of the worst things you can do to your house for heat," says Becci Taylor, director and UK Housing Property Lead at Arup.
The answer is not to abandon glass entirely. London still needs to make the most of daylight during the colder months. Instead, architects are learning to use it more intelligently, with smaller roof lights, better insulation, effective ventilation and external shading that stops heat entering in the first place. Tomorrow's buildings may look different, too. Rather than the flat facades that dominate many modern developments, Taylor expects architects to embrace more depth and texture, balconies, recessed windows and overhangs that cast shade naturally throughout the day.
Don't go back to black. The London skyline of the future will not just look greener. It may also look much whiter, too. Taylor points to cities such as Chicago and New York, where reflective white roofs are increasingly common. By bouncing sunlight back into the atmosphere rather than absorbing it, they can dramatically reduce how much heat buildings store during the day. "Painting your roof white can lower temperatures by several degrees," she says. "It's a really simple intervention." But not every roof needs to be white. Others will turn green. Dr Oscar Brousse, lecturer in urban climatology and health at University College London, points to the capital's growing collection of living roofs, from the biodiverse planting and beehives on top of the Museum of London to the rooftop gardens at the Barbican and 120 on Fenchurch Street, where trees, shrubs and flowering plants now sit above the City skyline. His team's research found that reflective white roofs cool cities more effectively than green roofs overall. But that does not mean green roofs lose out. "Green roofs have other benefits like biodiversity conservation, rainwater management and winter insulation," he says. "So the best solution depends on the building and what you're trying to achieve."
Self-cooling houses. It is all very well designing climate-friendly new buildings, but what about the one million existing London homes already thought to be at high risk of overheating? Retrofitting them is one of Sadiq Khan's top priorities. Air conditioning will almost certainly play a bigger role in London's future, particularly in hospitals and care homes. But it should not be seen as a silver bullet. "Heat that is inside has to go outside," says Brousse. "This can increase outdoor temperatures, creating feedback loops that ultimately increase the need for air conditioning." Instead, the priority should be preventing buildings from heating up in the first place. "We need to design and adapt buildings to be as cool as possible without relying only on air conditioning," says Petrou.
That means London homes borrowing ideas long familiar across southern Europe. External shutters, awnings and blinds stop the sun reaching the window, making them far more effective than closing curtains after the glass has already heated up. Better insulation, reflective or green roofs, reverse heat pumps and improved ventilation all help keep unwanted solar heat outside before it becomes trapped indoors. "They're not culturally part of the UK's design language yet," says Taylor, referring to external shutters. "But if we're expecting Mediterranean temperatures, we need to start designing for them." Much of that work will involve retrofitting homes that already exist. More than 1,000 London homes have already been upgraded through the Mayor's Warmer Homes programme, with plans to retrofit 16,000. But Anderson warns the pace is nowhere near fast enough. The capital is currently adapting homes around 10 times more slowly than needed, he says, while many previous retrofits focused on keeping homes warm in winter rather than cool in summer. Canadian retrofit programs face a similar gap between ambition and delivery.
Green and blue infrastructure
Ask Kate Sheldon what makes a city heat-ready and she starts with the 3-30-300 rule. This is championed by her charity Trees for Cities: everyone should be able to see at least three trees from their home, live in a neighbourhood with at least 30 per cent tree canopy, and be within 300 metres of a high-quality green space. Sheldon and the deputy mayor for the environment, Mete Coban, argue London needs to stop thinking of parks and trees as amenities and start treating them as climate infrastructure. That also means thinking beyond Hyde Park and Hampstead Heath. The priority is the greenery woven through everyday neighbourhoods: rain gardens on residential streets, trees outside schools, greener pavements and pocket parks that make walking and cycling bearable on the hottest days. "The density of central London isn't a barrier," says Sheldon, pointing to cities such as Paris and Atlanta where "you feel like you're in an incredible urban forest" despite their busy centres. Toronto and Montreal have adopted similar canopy targets, though progress remains uneven across neighbourhoods.
Her charity's latest campaign aims to ensure every school has at least three trees. It is an idea backed by science: air temperatures beneath trees are typically about 8C cooler than on exposed streets, and sometimes as much as 13C, while the shade they provide also helps cool surrounding buildings. "The great thing about neighbourhood interventions is they're doing lots of jobs at once," says Taylor. "Planting trees, rain gardens and greener streets are all things you'd want to do anyway. They improve biodiversity, make places nicer to live and help keep people cool." Protecting that greener city will increasingly rely on technology too. The London Fire Brigade says it is investing in drone technology to detect fires earlier and respond before they spread.
Cool commutes. A cool home is little comfort if the journey there still feels like an oven. In the future, navigating London during a heatwave may become less about finding the fastest route and more about finding the coolest one. Researchers at the IT University of Copenhagen have already developed CoolWalks, a navigation model that prioritises shade over speed, hinting at a future in which planners steer Londoners along cooler routes during heatwaves. Taylor imagines that evolving into a much richer layer of the city's transport network, helping people move between shaded streets, parks and cooling spaces rather than simply following the quickest route. The streets themselves may begin to change, too. Experts imagine more trees, shaded bus stops, drinking water fountains and pocket parks becoming part of the capital's "cooling infrastructure". Cyclists will need thinking about, too. Taylor says she increasingly finds herself commuting by bike during heatwaves, but dreams of a city where those journeys do not involve baking at every red light.
Then there is the Underground. While many of London's deep-level Tube lines were never designed with air conditioning in mind, TfL says it is already adapting the network for more frequent and severe heatwaves. Buses now feature reflective roofs, double-deckers have air-cooling systems, and Tube stations are gradually being upgraded with improved ventilation. For the trains themselves, air conditioning is likely to become increasingly unavoidable. The Elizabeth line and London Overground have already shown what cooler rail travel can look like. New air-conditioned DLR trains will begin entering service later this year, while the long-awaited Piccadilly line fleet will become the first deep Tube trains to feature AC when they enter service from December this year. The Bakerloo line is next in line for replacement.
Boost the blue. If trees become London's green infrastructure, rivers, ponds and fountains will become its blue infrastructure. That is certainly the direction of travel under the Mayor's ambition to make London a "swimmable city" by 2034, recognising that as temperatures rise, access to water will become as much about public health and climate resilience as leisure. Just as Paris has reopened the Seine to public swimming, London is beginning to rethink its own waterways. The opening of Sea Lanes Canary Wharf and the capital's first designated Thames bathing water at Ham hint at a future in which cooling off in natural water becomes an ordinary part of surviving the hottest weeks of the year. Sea Lanes' founders hope their floating lido will become a blueprint for similar projects, while plans are also under way for the community-led East London Waterworks Park in Waltham Forest, where natural swimming ponds would sit alongside wetlands and biodiverse green space. Canadian waterfront cities from Vancouver to Halifax are exploring similar river and lake access projects.
But becoming a swimmable city means becoming a safer one, too. The London Fire Brigade says it plans to install more throw lines and lifesaving equipment at popular waterways, alongside wider public education campaigns to help people understand the risks of swimming in open water. Blue infrastructure extends well beyond places to swim. There are already around 4,000 free water refill points and more than 100 public drinking fountains across the capital, with more planned. Taylor would also like to see many more water features incorporated into London's public spaces, pointing to the fountains at Granary Square in King's Cross and the splash park at Elephant Park. "These generate quite a bit of cooling," she says. "We should think about water features wherever it's practical."
New daily rhythms. London's buildings will not be the only things adapting to a hotter climate, Londoners themselves may have to adapt too. The first signs are already here. During last month's record heatwave, Plashet School in Newham introduced a "heatwave protocol", moving lessons into the cooler morning hours before ending the school day at 1.30pm to avoid the afternoon heat. Pupils were told to stay in the shade, PE and other heat-generating activities were scaled back, and classes were moved from upper floors to cooler ground-floor classrooms. Workplaces are evolving too. Britain's workplace regulator, the Health and Safety Executive, now advises employers to consider flexible working patterns, while the Trades Union Congress has urged businesses to allow earlier starts, later finishes and home working during heatwaves. Canadian labour boards are issuing similar guidance as heat events become more frequent.
The accessories of a London commuter may change, as well: handheld misters, rechargeable neck fans, long a familiar sight on the streets of Tokyo and Seoul, and even the occasional parasol could become as commonplace in July as umbrellas are in November.