The warning comes from researchers at Imperial College London and the World Weather Attribution group, who say such extreme heat would have been virtually impossible without the impact of global warming.
Saturday's heat, which may persist above 28°C for three consecutive days, would once have been expected only once every 2,500 years under pre-industrial climate conditions. Scientists now warn that Britain is entering a dangerous new era of "silent killer" heatwaves that could take a growing toll on lives, infrastructure, and public health.
"This simply wouldn't have been a heatwave without human-induced warming," said Dr Ben Clarke of Imperial College London. "With every fraction of a degree of warming, the UK will face hotter and more hazardous conditions."
Mounting risks to health and infrastructure
Prolonged heatwaves are particularly dangerous because they leave little time for the body to recover. The UK Health Security Agency recorded over 10,000 premature deaths during summer heatwaves between 2020 and 2024, and experts say this weekend's temperatures could again be fatal for older and medically vulnerable people.
According to Dr Friederike Otto, also at Imperial College, the UK remains dangerously unprepared for rising summer temperatures. "Heatwaves are still severely underestimated," she said. "This kind of heat in early summer should be a wake-up call."
A report by the UK's official Climate Change Committee in April described current adaptation efforts as "inadequate, piecemeal and disjointed."
"Extreme heat is already costing British lives," said Prof Mike Tipton, an expert in human physiology at the University of Portsmouth. "Until we cut emissions, these events will only grow more severe."
Wildfire risk and home overheating on the rise
Soaring temperatures combined with unusually dry spring conditions have also raised the risk of wildfires, warned Theodore Keeping, a climate scientist at Imperial. "We've already seen the largest burnt area on record in the UK this year," he said, urging caution with outdoor fires, barbecues, and cigarette disposal.
A separate study estimates that 80% of UK homes overheat in summer, particularly properties not designed to cope with prolonged high temperatures. Experts advise keeping windows and curtains closed during the day and opening them at night to cool indoor spaces.
Heatwaves set to become the norm
UK temperatures topped 40°C for the first time in 2022, and the Met Office now says there is a 50% chance of reaching that level again within the next 12 years. It also warned that 45°C is within the realm of possibility.
The impact of extreme heat goes beyond human health. According to a recent report by Swiss Re, heatwaves are now deadlier than floods, earthquakes, and hurricanes combined—responsible for up to 500,000 deaths globally each year.
"Extreme heat used to be considered an invisible peril," said Jérôme Haegeli, chief economist at Swiss Re. "But the risks are real and rising—affecting human life, our economy, infrastructure, and health systems."
As carbon emissions continue to rise, scientists stress that early summer heatwaves like this one will become increasingly frequent, deadly, and disruptive—unless urgent action is taken to reduce greenhouse gases and invest in adaptation.