London Climate Action Week was supposed to be a confab to figure out how to lower emissions. Instead, it’s a textbook example of how the world is being forced to adapt to increasingly extreme heat.

“London isn't just calling – it's cooking,” said United Nations Secretary-General Antonio Guterres on Tuesday, while giving a keynote speech at the event.

The UK Met Office is expecting temperatures to reach 39 degrees Celsius (102 degrees Fahrenheit) on Wednesday, a mark that would smash the June record and flirt with the hottest temperature ever recorded in the country. The UK isn’t alone: a deadly heatwave is sweeping across Europe, with countries shuttering schools and nuclear plants and rail operators curtailing operations to avoid overheating tracks.

“Our infrastructure is not set up for this temperature,” says Katie Glaze, sustainability director for infrastructure consultancy Brookbanks. She pulled out of around nine sessions on how to adapt buildings for extreme climate due to transport issues. “The irony is that a lot of the conferences I was going to attend, the topic of discussion is what is happening now,” she adds. “It’s all very future-thinking, but we have the situation now that we’re not addressing quickly enough.”

Europe is currently enveloped by an area of slow-moving high-pressure air. This traps warm air like a “lid on a pot” and creates a “heat dome” which blocks other weather fronts, like clouds and rain, from moving through. The air becomes hotter and hotter while the ground also warms, loses moisture, and becomes easier to heat even more. A higher starting temperature amid global warming has intensified the effect.

In London, organizers on Tuesday canceled an event on extreme heat because the library it would be hosted in doesn’t have air conditioning. The “very unpleasant” indoor conditions and hot journeys to the venue would have risked the wellbeing of speakers and guests, host the Zurich Climate Resilience Alliance says.

Earthwatch Europe, meanwhile, called off events for families to explore local wildlife in Hammersmith Park “in a twist nobody wanted, but everyone can appreciate the irony of,” the charity writes in a post on Facebook.

The festival was expected to attract 75,000 people across more than 1,000 events over nine days. But some attendees have chosen to stay away due to heat-related health concerns. London, like most cities, traps more heat than rural areas due to the high density of heat-absorbing material like concrete and tarmac and a lack of cooling vegetation.

Co-director of the Climate Majority Project Rupert Read decided not to go to London for the event because he has a heart condition, which can be exacerbated by heat. His organization moved events online.

“It is unbelievable that it has come to this,” he says, adding that London Climate Action Week will continue “with a sense of very real jeopardy hanging over it, because that is the reality now. This is climate breakdown in action.”

The UK government has warned the heatwave will strain public health systems and raise the risk of disease or even death. Last year, the government counted more than 1,500 heat-linked deaths across the country, with the elderly being the most vulnerable age group.

Charlotte Baker, who runs her own environment and public health consultancy and lives outside London, also canceled plans to attend a conference on making cities more liveable this week because she has severe asthma triggered by pollen and air pollution. She was hospitalised by an asthma attack three years ago in high temperatures and doesn’t want to risk a repeat given the forecast of stagnant hot air that will trap air pollution.

“I’m really gutted,” she tells WIRED. “This is a really difficult decision for people with health conditions, and especially if you think you’re going to miss out on potential networking or opportunities for work.”

Train operators have advised against all but essential travel and warned of disruptions as heat can cause overhead powerlines to sag, steel rails to buckle, and signalling systems to fail. Several London lines were already experiencing problems on Tuesday morning due to flooding from an overnight thunderstorm fueled by the same heat dome responsible for the rocketing temperatures.

Russ Avery, who runs his own communications business, recalls being stuck on a packed train without functioning air conditioning in a previous heatwave. An analysis by Bloomberg last year found the Tube’s train cars can be up to 5 degrees Celsius hotter than the air outside.

“It was genuinely really scary,” Avery says. Reluctant to put himself in that situation again, he decided not to attend the week’s flagship event despite the potential to make new clients and meet with older ones he rarely sees in person. “Everyone knows how horrible the Tube is when it’s this kind of temperature, and that things can go wrong there,” he says.

Even those with their own vehicles won’t rely on the infrastructure to hold up against the heat. Founder of My Green Pension, Claire Bishop, had planned to drive the two-and-a-half hours from Bristol in South West England in her electric vehicle, hoping to attract business opportunities. She’d already paid for a booth at the main event and a banner, leaflets, and a parking space, but she canceled due to concerns about being stuck on a motorway in the heat and the road surfaces softening and becoming sticky under the heat.

With schools shutting down due to the heat, Bishop also has to handle childcare. “It was all those unknowns for me that I just have to consider if that risk is worth taking,” she says.

Limited access to rapid charging hubs means Glaze wouldn’t have been able to drive in her electric vehicle to London without stopping multiple times, “You almost have to laugh", she says. Missing the event could mean a “loss of earnings,” for her, citing meetings she had lined up with developers and a client.

“We‘ve spent too long talking about climate change and action”’ Glaze says, “but today’s a perfect example of how we’ve failed.” She adds: “We haven’t addressed climate change quick enough. The reality is here – we are unprepared.”