LONDON — When storm clouds rolled into London on Tuesday evening, the rain brought with it much-needed relief for sweltering city residents after a day of record-breaking heat that drove wildfires, disrupted train travel and strained the city’s infrastructure and health services.
The heat had cleared on Wednesday but it left behind a city newly full of anxieties about how London and other European cities can cope with the rising frequency of such extreme weather events.
Philipp Rode, the executive director of LSE Cities, a research center at the London School of Economics, said that criticism ahead of the heat wave that warnings from meteorologists, the media, urban planners and climate scientists were “hysterical” proved to be false on Tuesday.
“That idea has been completely debunked, because the effects are fairly dramatic,” Dr. Rode said. “Particularly the fires became very symbolic for not just the unpreparedness, but also for not really appreciating what has been said for decades — that this would happen.”
The heat wave led to huge wildfires in France, Spain, Italy and Greece, and parts of England reached 40 degrees Celsius — 104 Fahrenheit — for the first time on record Tuesday, while Paris hit that mark for only the third time.
It is part of a worrying trend, driven by global warming, with temperatures worldwide on average about 2 degrees Fahrenheit higher than the late 19th century, before emissions of carbon dioxide and other heat-trapping gases became widespread. Scientists say that heat waves have increased in frequency and intensity faster in Europe than in almost any other part of the planet.
London and other European cities at northern latitudes, where historically heat was a rare threat but cold a frequent one, need to adapt to remain livable, Dr. Rode said.
“We have prepared a very sophisticated infrastructure system, the railways, the energy systems, all the way to how we design school buildings and hospitals — for very specific climate,” he said, with planning across Britain around a temperature span of around negative 10 to 35 degrees Celsius. “And yesterday, we exceeded that, and that then results in these collapses.”
London Ambulance Service said in a statement that there was a sustained demand for its service, which put the organization under “extreme pressure,” as a direct result of the heat wave. Early data showed that on Tuesday, there was a tenfold increase in emergency calls to treat heat exposure incidents compared with the week previous.
Sadiq Khan, the mayor of London, said on Wednesday morning that Tuesday was the city fire service’s busiest day since World War II. Fire destroyed some 41 properties, many of them near grassy areas that had turned to kindling in the brutal heat, allowing blazes to spread quickly.
“It shows the consequences of climate change with temperatures exceeding 40 degrees,” Mr. Khan said in an interview with BBC News.
Firefighters and their union said years of underfunding had left them woefully unprepared, with some crews on duty for as long as 14 hours without breaks, food or water, and no backup available. London’s Fire Brigade said staffing shortages left more than one-quarter of its fire engines out of service on Tuesday.
At times every engine in service was in use — not a single one was left to respond to a new emergency, a union official said.
Extreme weather fueled by climate change has also hit European cities with severe flooding. A year ago, fierce summer storms wreaked havoc from Britain to Croatia. Western Germany was hardest hit, with nearly 200 people killed, and London saw a month’s worth of rain in one day, bringing much of the city to a standstill.
Dr. Rode noted that there has been little political will to engage with the issue of extreme heat, as there would be in places like Australia or California where damaging wildfires occur regularly.
“But here we don’t have that, so I think what can we hope for is that it’s a wake-up call,” he said. “People must appreciate that while you can of course prepare better, this is just a taste of what’s to come.”
Homes in northern Europe were largely built to retain heat, not dissipate it, and many are poorly ventilated. In a dense city like London, poor air quality, abundant pavement and a relative absence of greenery all reinforce each other’s effects, said Léan Doody, who leads the integrated cities and planning network for Europe for Arup, a British engineering firm.
Yet major cities remain largely unprepared for this new reality of extremes, leaving city officials struggling to respond.
“I think things need to happen a lot quicker,” Ms. Doody said. “It should be well known that there are these risks, but I think that it’s like everything — the day-to-day takes over.”
A spokesperson for the London mayor’s office said in a statement that he “has been clear that urgent action to combat climate change is needed and he is already taking some of the most radical action of any world city to adapt London to our changing climate.”
But, the statement added that the British national government has “been underprepared for this heat event and the fact that we are already facing the impacts of climate change,” and it said that action was needed now to “tackle the risk of overheating in London.”
The mayor’s office said it worked with local authorities across the city to ensure that the most vulnerable residents had access to somewhere to cool down during the heat wave. Its “London Plan,” a longer-term development blueprint for the city, encourages builders to design for extreme weather scenarios.
Cities, where natural landscapes have been replaced with densely packed buildings, concrete and blacktop, get hotter and retain heat longer than surrounding areas — the “urban heat island” effect, a major concern as the climate warms.
England’s broader heat wave plan, published by the government this month, includes advice to individuals on how to stay safe and guidance on how to protect infrastructure.
But critics say it doesn’t go far enough toward addressing the issue with the kind of urgency that is needed. And if greenhouse emissions aren’t drastically curbed, no amount of altering cities will be enough, Dr. Rode said.
“Adaptation at some point has physical boundaries,” he said. “There are certain conditions, which you simply, with all the intelligence and all the investments we have and the technology, where it exceeds our capacity to adapt.”
This week’s heat made it clear that even adaptation has barely begun. Nursing homes, many in older, poorly ventilated buildings, struggled to keep residents hydrated and cool. Parents wrestled with whether it was safer to keep their children in overheated apartments or send them to overheated schools.
London’s Tube network can be stifling on an ordinary summer day — most of the trains do not have air-conditioning, and older tunnels have few ventilation shafts. In a heat wave, the system can become unbearably hot.
Train tracks can expand, warp and buckle in extreme heat, a danger that forced cancellation of some rail services this week and prompted others to operate at reduced speed. On the heels of that disruption, Britain’s rail network started a task force on how to withstand future heat waves — addressing a long-anticipated crisis after it has arrived.
Simon Fox, an academic who was stranded in London for two days after his train to Leeds was canceled, said he felt the “tired resignation of a population all too used to a decaying infrastructure.”
Mr. Fox was again waiting for a train in Kings Cross station on Wednesday, along with a crowd of others trying to find a way to continue their journeys amid severe delays.
“One warm gust was all it took to make it tumble,” he said.
Isabella Kwai and Euan Ward contributed reporting.