The joint highest temperature recorded so far in 2023 was reached on Sunday, but conditions are already changing.
Coningsby in Lincolnshire reached 32.2°C, matching the same heights seen in Chertsey, Surrey, on June 10.
Meanwhile, thunderstorms have hit areas in the north of England, Scotland and Northern Ireland, and next week is looking much cooler across the UK.
BBC Weather’s Tomasz Schafernaker said Sunday’s heat “marked the end of our current heatwave.”
He continued: “The end of the month is looking considerably cooler, but we’re still on track for one of the warmest Junes in the UK since records began.
“Some parts of England have been experiencing temperatures similar to the Mediterranean for more than two weeks.
“The weather has also been consistently warmer than average in other parts of Europe.”
The Met Office said Sunday’s maximum temperature in Coningsby was recorded at the same spot as the UK’s hottest day, when it hit 40.3C on July 19 last year during an extreme heatwave.
Yellow weather warnings for thunderstorms were in effect across much of the northern part of the country through the afternoon, with many reporting downpours and hail.
As the south sizzled, storm clouds were gathering further north
But as black clouds rumbled their way across north-east Scotland and out to sea, temperatures continued to rise in the south.
London Fire Brigade said 10 fire trucks and around 70 firefighters were dispatched to tackle a grass fire that had engulfed two hectares of land at Rammey Marsh in Enfield, north London.
And New Wimbledon Theater was forced to cancel a performance of Charlie And The Chocolate Factory the Musical due to the “impact on stage working conditions”.
Monday is expected to be windy with clouds and showers in the north and west of the country, with more unstable conditions in the forecast for many in the coming days.