The hottest day of the year so far has been recorded in England, Northern Ireland, Scotland and Wales and forecasters believe it is going to get even hotter.
It was the hottest day on record in Northern Ireland with 31.2C recorded in Ballywatticock, in County Down, at 3.40pm, beating the previous highest temperature of 30.8C, reached on July 12 1983 and June 30 1976.
In England, 30.7C was recorded at Linton-on-Ouse, North Yorkshire, on Saturday, surpassing the 29.7C recorded in south-west London on June 14.
The year's highest temperatures so far were also recorded in Usk, Monmouthshire, Wales, at 29.0C, and in Threave, in the Dumfries and Galloway region of Scotland, at 28.2C.
But the Met Office said that temperatures could get even higher in England and south Wales on Sunday as the summer heatwave continues.
Tom Morgan, meteorologist at the Met Office, said: "Temperatures are expected to increase even further on Sunday, reaching highs of 33C in the south of the UK."
He added an extended hot spell of weather is expected to last for much of the week ahead, adding: "It's going to mean that people are really going to feel the effects of the heat as we go through this week."
Thousands have flocked to beaches across the country, including Bournemouth beach in Dorset with people seen cooling off on surf boards and inflatables in the sea.