According to provisional figures released by the Met Office, the national average temperature between 1 June and 31 August reached 16.10°C. That is 1.51°C above the long-term seasonal average and higher than the previous record of 15.76°C, set in 2018.
The milestone pushes the once-legendary summer of 1976 out of the country's top five hottest seasons. Notably, all five of the UK's warmest summers have occurred since 2000, underscoring the accelerating impact of climate change.
A summer defined by relentless heat
The summer of 2025 was marked not by a single searing heatwave but by four separate periods of extreme heat. In each, temperatures surpassed 30°C for several consecutive days.
The highest reading was 35.8°C in Faversham, Kent, a few degrees shy of the UK's all-time record of 40.3°C set in 2022. But what drove this year's average so high was not isolated peaks — it was the persistence of heat over weeks.
England recorded its warmest June in history, while Wales logged its third warmest. By the end of June, scientists from the World Weather Attribution (WWA) group concluded that the heat in south-east England was made 100 times more likely by climate change.
July continued the trend, ranking as the UK's fifth warmest July on record, before a late-summer heatwave in August sealed the season's place in history.
Dr Emily Carlisle of the Met Office said the pattern was driven by a triple combination of stubborn high-pressure systems, unusually warm seas around the British Isles, and parched spring soils.
"These conditions created an environment where heat built quickly and lingered, with both daytime highs and night-time lows significantly above average," she explained.
The toll of heat and drought
Rainfall across the UK fell to just 84% of the seasonal average. England, in particular, faced what officials described as "nationally significant" water shortages. Farmers reported widespread crop failures, and much of the country saw restrictions on water use as reservoirs and groundwater reserves ran low.
The prolonged dry spell has raised concerns about the UK's preparedness for climate-driven extremes. Water companies have faced renewed criticism for underinvestment in infrastructure, while farming groups are calling for long-term adaptation strategies to protect food security.
Climate change driving record summers
Met Office scientists say the summer of 2025 illustrates how quickly human-induced climate change is reshaping the UK's climate baseline.
A rapid attribution study concluded that a summer as hot as this one is now 70 times more likely than it would have been without human greenhouse gas emissions. In a pre-industrial climate, such a summer might have occurred once every 340 years. Now, researchers estimate, it can be expected roughly once every five years.
Dr Mark McCarthy, head of climate attribution at the Met Office, said even hotter summers are plausible in the near future.
"What would once have been considered an extreme is increasingly becoming the norm in today's climate," he said.
The findings echo earlier Met Office projections: in 2019, scientists predicted that a summer like 2018 could occur every eight to nine years under current warming levels. That forecast has already been borne out, with 2025 surpassing 2018 just seven years later.
A new definition of ‘normal'
Climate experts warn that the UK's perception of "exceptional" summer weather is being rapidly rewritten.
"The notion of what is extreme is shifting before our eyes," said Dr McCarthy. "What the public once thought of as a once-in-a-lifetime heatwave is now part of a new normal."
With global greenhouse gas emissions still climbing, the Met Office and WWA stress that future summers could bring even more dangerous extremes — making adaptation in infrastructure, water management, and agriculture increasingly urgent.