Scotland and Northern Ireland will be a little cooler, but even eastern parts of Scotland will reach the low twenties at times.
She said: We've got two records to break this bank holiday weekend.
And Monday will also be good, although slightly cooler.
The May Bank Holiday was introduced in 1978 and the temperature has never topped the 28C mark since then.
Met Office forecaster Craig Snell said the South East, East Anglia and the East Midlands will feel the heat most.
The weather is set to become mixed as the month progresses, and the May 19 wedding of Prince Harry and Meghan Markle draws near.
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Mr Snell said: "It looks likely we'll at least see our warmest Bank Holiday Monday on record on Monday".
He added: "Edinburgh should therefore see another lovely day, while we believe some fog could affect the south west coast, near Stranraer".
There will be a drop off in temperature as the week goes on, though the warmth is expected to return midway through the following week.
"High pressure is over the United Kingdom at the moment meaning the temperature just goes up and up and up".
"Neither does it look like it's going to be a complete washout, frightful end to the month of May".
We are being told to expect warm weather for the long weekend - but not much sunshine.
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BBC weather forecaster Alina Jenkins said: "The early May Bank Holiday temperature record has just been broken".
"That's going to be the exception rather than the rule".
Warm temperatures in the 70s Fahrenheit, or 20s Celsius, are expected across England and Wales from Saturday through until Tuesday.
Scots managed to enjoy some well-deserved sun as temperatures soared over the bank holiday weekend.
The Met Office said the conditions are being caused by an area of high pressure which is due to dominate southern Britain over the coming week.
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