Temperatures are set to soar to 30C (86F), with forecasters predicting that Wednesday could become the hottest day of 2018.
If Britain does hit 30C it will be as hot as Gibraltar and parts of southern Spain, such as Marbella, according to forecasts.
The weekend looks set to be sunny throughout.
Martin Bowles, operational meteorologist at the Met Office, said: “There’s widespread sunshine for several days due.
“Over the weekend it’s going to stay sunny across the board almost everywhere.
“The temperature will be up a little bit each day.”
Saturday will see highs of 24C (75F) and temperatures on Sunday could hit 25C (77F) in the South East and London, with temperatures across the country rising, Mr Bowles said.
Sky weather producer Chris England said: “It’ll be turning hotter over the next few days, with plenty of sunshine when the sun is at its highest, probably reaching around 30C (86F) somewhere in the South East.”
The average for this time of year is about 21C (70F) in London, 18C (64F) in Manchester and 17C (62F) in Scotland.
“We’re going to be widely four or five degrees above [the average] tomorrow and the next day,” Mr Bowles said on Friday.
“I’d say more likely than not that somewhere in the UK on Wednesday will get 30C, probably the South East of England,” he said.
In June last year, temperatures reached 34.5C (94F). The record was in June 1976, when the mercury hit a record-setting 35.6C (96F).
Temperatures reached 29.1C (84F) in London in April this year.