The Met Office said high pressure building across the country will bring warm and humid conditions.
Temperatures could soar to 30C next week with a spell of warmer weather set to hit the UK, forecasters say.
The Met Office said high pressure building across the country will bring warm and humid conditions, with temperatures climbing above the seasonal average and reaching the high-20s or possibly 30C by Friday.
It means parts of the country could be warmer than Los Angeles by the end of next week.
There were highs of 22.4C in Kent on Saturday, while London’s Kew Gardens reached 21.3C.
Sunday is expected to be fine and dry for most of the UK, with only a few showers across Scotland.
The highest temperatures are forecast in south-west England, where highs of 26C and an isolated 27C are possible.
Wales is expected to enjoy temperatures of around 23C on Sunday, while Scotland will become warmer after a showery Saturday, with highs of around 20C.
There may be some thunderstorms in parts of the country on Monday, although temperatures should remain in the low 20s before cloud and rain spreads from the west on Tuesday.
However, forecasters say the heat will increase from the middle of the week as warmer air from Europe moves into the UK.
On Wednesday, temperatures in south-east England could reach around 27C, with another surge of warmth expected on Thursday and Friday and into next weekend.
While cloud cover could affect the highest temperatures, forecasters say there is a chance of 30C being recorded by the end of the week.
Met Office forecaster Kathryn Chalk said: “We’re definitely seeing a warming trend from midweek onwards.”
She added: “Relatively warm and humid nights are also on the cards- not as expected as what we had a few weeks ago, because it won’t be wall-to-wall sunshine like that, we had a stronger signal for that compared to this, but nevertheless it is going to be turning warmer.”
