Wednesday could see the hottest day of the year so far - as temperatures may reach as high as 25C (77F) in the South East.
Tuesday was the warmest this year, with 20.9C (69.6F) recorded in Santon Downham, Suffolk, but the mercury is set to rise even further on Wednesday.
At 25C, the temperature is expected to be more than 10C higher than the UK average for the time of year.
The high temperatures will not just be confined to one part of the country, with 20C-21C (68F-70F) expected in Newcastle, 18C-19C (64F-66F) in Northern Ireland and 17C (63F) in Glasgow.
Met Office meteorologist Mark Wilson said: "It's going to be a pretty nice day - it will be a slow start in places with cloud first thing.
"But by mid-afternoon there will be lots of unbroken sunshine."
Thursday could see even higher temperatures - 25C-26C (77-79F) in the South East - as warm air continues to come up through Spain and on to the UK.
Saturday could see isolated showers in parts, while there is "uncertainty" about what Sunday's weather will bring.