Summer 2025 set to be hottest on University records

Repeated spells of hot or very hot weather in each of the three summer months - June, July and August – has meant that summer 2025 has recorded the highest average temperature for any summer on the University of Reading’s records, which go back to 1908.

June 2025 was the warmest on our records, July was the fourth warmest, and August was less warm, but still provisionally above current climate averages.

The summer months saw three heatwaves - in which three or more consecutive days surpass 27 °C - with the longest being five days between 9-13 July. 

Dr Stephen Burt, meteorologist at the University of Reading, said: “Based on provisional figures for the next few days, by daily mean temperature, summer 2025 stands as the hottest on our records. 

“In terms of mean daily maximum temperature, summer 1976 remains at the top of the table (mean 24.68 °C), while summer 2025 slips down to fifth place (currently 24.27 °C) owing to no exceptionally hot days - the hottest day this summer was 32.4 °C on 12 August. In all, 35 days surpassed 25 °C, and eight 30 °C.”

Rain and sunshine

 As of the afternoon of Wednesday, 27 August, only 4 mm of rain has fallen at the University of Reading Atmospheric Observatory, making August the second-driest on record to date.

Dr Stephen Burt said: “June saw only 23 mm of rain fall, and July 44 mm. More than half of July's rainfall fell in thunderstorms on 31 July, including 12 mm in 8 minutes in an early evening storm. 

“Summer 2025 with only 72 mm to date would rank in the 'Top 10 driest'. However, forecasts suggest 20-25 mm likely to fall in the next few days, but even if this is correct, the month's total rainfall will amount to about half of August's average.”

June 2025 had 130% of its average sunshine, with 253 hours recorded. Estimates for sunshine amounts over the coming days suggest a summer total around 690 hours in all, which ranks within the 'Top 10 sunniest' since the sunshine record began in 1956, but a long way behind 1976 (843 hours) and 1959 (808 hours).

Expert comment - the impacts of hotter weather

Dr Jess Neumann, associate professor of hydrology at the University of Reading, comments on the impact extreme heat has on people and the environment: 

“Many would say that this has been a “good UK summer” with lots of warm and dry weather painting a picture of ice creams, beach days and BBQs in the sunshine. 

“However this is not the case for everyone and recent studies indicate that there have been hundreds of heat-related deaths during the UK summer heatwaves. 

"It’s not just during days of extreme heat that people are affected, but consistently above average temperatures throughout the day and night can put pressure on the human body, leading to health conditions such as dehydration, headaches and heat exhaustion. 

“The lack of rainfall has also had a knock-on effect to public water supply, agriculture and the environment. Hosepipe bans are still in place across parts of the country, farmers have had to harvest crops early due to drought, pollutants in rivers are at critical levels and wildlife is suffering due to a lack of freshwater. 

“Parts of the UK will be in significant trouble if a dry winter follows this summer, as we desperately need rainfall to restock our rivers and reservoirs and recharge our aquifers.

“Whilst on the face of it, a hot and dry summer may be viewed as a good thing by some, in the long term it raises serious questions about where we need to invest in infrastructure, how we manage our water, and what we will need to do to cope with a changing climate.”