The weekend is set to be the hottest of the year so far, with temperatures of 26C "a fairly safe bet" in some parts on the country on Sunday.
Saturday was the warmest day of the year so far, but Sunday is set to be even hotter.
Temperatures hit 24.9C in Santon Downham, Suffolk, but 26C is expected and a "fairly safe bet" for the same region on Sunday, according to Met Office forecaster Tom Crocker.
The bookies slashed their odds for Sunday's forecast as areas in southern and eastern parts of the UK look set to be bathed in such temperatures.
Mr Crocker said forecasters were "fairly confident" that Sunday would beat the top temperatures and "the majority of the country will see a dry day with plenty of sunshine".
Ladbrokes said bets had been pouring in and are offering 2/1 for the mercury to reach 30C or higher before the weekend is out.
Jessica Bridge of Ladbrokes said: "It's getting hotter by the day and punters are convinced the sunshine's here to stay all summer."
Pollution levels are expected to peak on Sunday, with high levels possible locally and widespread moderate air pollution.
Those heading outdoors to enjoy the fine weather are also warned to be aware that UV levels will be high.
Mr Crocker pointed out there is a "reasonable possibility" that people can get burnt if they are not protected.
The exposure category is high so people should seek shade during the midday hours from around 11am to 3pm. They are urged to cover-up and wear sunscreen.
This will be the last of the warm spell as the new week will be cloudier, cooler and have will bring on the rain.
From Monday temperatures in Wales may be around 17-23C, around 18-19C in Northern Ireland and easterly breezes in areas like Aberdeen will bring 15-16C temperatures to parts of Scotland.
As the week progresses, temperatures are still likely to be mild, but will fall day on day.