The UK could enjoy the hottest day of the year before thunderstorms threaten to bring flooding and travel disruption later in the week.
Temperatures of up to 29C are forecast for the South East of England on Monday, which would surpass the 28.3C seen in Northolt, west London, on 2 June.
The Met Office said Sunday narrowly missed out on hitting that mark, with 28C recorded at Heathrow and St James' Park in London.
However that did not appear to dampen the enthusiasm of England football fans who watched their team win their opening match against Croatia at Euro 2020 in the blazing sunshine at Wembley stadium.
Elsewhere temperatures reached 24C at Fyvie Castle in Aberdeenshire, with 25.3C recorded both at Hawarden Airport in Wales and on Northern Ireland's Giant's Causeway.
Monday is due to stay very warm and sunny, though breezy winds and scattered showers are forecast for the north of the UK while Scotland take on the Czech Republic at Hampden Park in Glasgow.
Meteorologist Annie Shuttleworth said: "We are forecasting that 29C could be the maximum tomorrow. If we do see that 29C, it would be the warmest day of they year so far and it would be in the South East.
"It will be another day of warm weather and it could be just one degree warmer."
Fresher weather will develop over Tuesday before a "thundery breakdown" brings heavy rain from Wednesday.
The Met Office has issued a yellow weather warning for thunderstorms across much of England and Wales between 6pm on Wednesday and 6am on Friday.
Some areas could see as much as 5cm of rainfall within a two-hour period.
"There is a small chance that homes and businesses could be flooded quickly, with damage to some buildings from floodwater, lightning strikes, hail and strong winds," a Met Office spokesperson said.
"Where flooding or lightning strikes occur, there is a chance of delays and some cancellations to train and bus services. There is a small chance that some communities become cut off by flooded roads."
The thunderstorms are expected to move north-east across parts of England and Wales over this period, although their exact location and timing remains unclear.
Additional reporting by Press Association