A hot Saturday for some will be followed by cloud and rain on Sunday in a mixed weekend.
The best of the sunshine will be in south-east England on Saturday, with sizzling temperatures and little wind, while the rest of the UK will be fairly cloudy.
However, rain is expected across parts of the the west and Scotland on Sunday, with a chance of thunderstorms.
The south east of England is expected to stay warm, with highs of 25C (77C).
The difference between the two days is down to the high pressure which will dominate much of Saturday being replaced by low pressure on Sunday.
Met Office Forecaster Nicola Maxi said: “There will be a bit of coastal fog in south England and Wales on Saturday morning but the day should be very warm.
“The south east will hang on to that warm, dry weather on Sunday, while the west starts to see a build-up of cloud, with rain later on.
“Scotland will see a few showers across both days, and the same in the north on Sunday.”
Temperatures in London will reach highs of 26C (78.8F) on Saturday, and 24C (75.2F) the following day, accompanied by light rain in the evening.
Most of Scotland will be cloudy on Saturday, with highs of 16C (60.8F), but will see heavy rain on Sunday morning.
Northern England should stay around 18C (64.4F) on both days.
The average temperature for June is 17C (62.6F) and its likely that most of the UK should be warmer on Saturday.