As the UK prepares for a heatwave this week, there is a 50/50 chance of a day where temperatures reach 40C within the next 12 years, the Met Office has predicted.
It said the prospect of exceeding that figure is now more than 20 times more likely than it was in the 1960s, as a result of climate change.
The UK had its first recorded temperature above that threshold on 19 July 2022, when it was 40.3C in Coningsby, Lincolnshire — the hottest day in British history.
And while temperatures will not get that high this week, the Met Office has said a heatwave is likely in many parts of England, with a maximum of 33C forecast in the east on Sunday.
Met Office spokesperson Grahame Madge told Yahoo News that warm air driven from southern Europe later this week will make it very warm in the UK.
“This week the UK will experience rising temperatures,” he said. “Later in the week, a weather pattern develops which will encourage a flow of air from further south in Europe to bring much warmer conditions to the UK, with values expected to reach 32C on Saturday.”
The Met Office said much of the UK will reach the threshold for a heatwave either on Friday or Saturday.
To qualify as a heatwave, there must be three continuous days of temperatures at a certain level, which varies by area in the UK.
Madge said: “A heatwave is a period of three days or more where the maximum temperature reaches or exceeds a specific threshold.
“This threshold is 25C for northern and western parts of the UK, rising to 28C for Greater London and parts of the Home Counties.”
Have UK summers been getting hotter?
The Met Office predicted that the UK is likely to experience a hotter than usual summer in its most recent three-month outlook, after this year’s spring was the sunniest and among the driest and warmest on record.
Four of the five warmest summers on record for England have occurred since 2003, while all of the top 10 warmest years according to mean temperature have occurred since the year 2000, with five in the most recent decade up to 2024.
Records extending back to 1890 show that the mean temperature (the average of the maximum and minimum temperature across every weather station through the year) has risen from just over 7.5C in 1890 to more than 9.5C today.
What is causing this?
Climate change, caused by greenhouse gas emissions, has made heatwaves 30 times more likely in the UK, the Met Office has said.
Over time, this will make UK winters warmer and wetter, while summers will become hotter and drier, although wetter summers will be seen sometimes. By the year 2050, heatwaves similar to the one seen in 2018 will happen every other year.
Met Office scientist Emily Carlisle said earlier this month: “The UK’s climate continues to change.
“The data clearly shows that recent decades have been warmer, sunnier, and often drier than the 20th century average, although natural variation will continue to play a role in the UK’s weather.”
How hot will it get in the future?
In its study on 40C temperatures, published in Weather Journal on Wednesday, the Met Office warned that even higher temperatures of 45C or more “may be possible” in today’s climate, while heatwaves could go on for a month or more.
The study said the chance of temperatures hitting 40C is more than 20 times more likely than it was in the 1960s, and has almost trebled since the year 2000.
Temperatures several degrees higher than the July 2022 record – up to a maximum of 46.6C – are also “plausible”.
Dr Gillian Kay, senior scientist at the Met Office and lead author of the study, said: “Because our climate continues to warm, we can expect the chance to keep rising. We estimate a 50/50 chance of seeing a 40C day again in the next 12 years.
“We also found that temperatures several degrees higher than we saw in July 2022 are possible in today’s climate.”
The Met Office predicts that by the year 2070, summers will be between 1C and 6C warmer and up to 60% drier, and winters will also be up to 4.5C warmer and up to 30% wetter.
