Portsmouth is set to enjoy some early summer sunshine next week, with the mercury expected to rise up to 23C in the south east.
After a weekend of cloudy weather and scattered showers across the UK, forecasters are predicting the region could bask in warm temperatures on Monday, well above the average for May.
Across the south east corner of England there will be sunny spellsMeteoGroup forecaster Andy Ratcliffe
But experts have warned the good weather is not set to last, with “unstable” conditions arriving across much of the country from Wednesday.
MeteoGroup forecaster Andy Ratcliffe said: “The South East could see highs of 23C (73.4F) on Monday. It won’t be as warm in the north and west of the UK, where it will be more like 14C (57.2F) to 17C (62.6C).
“Across the south east corner of England there will be sunny spells, while there is a risk of heavy showers in north and west of the UK.
“We’re looking at highs of 20C (68C) in the South East on Tuesday but generally as the week goes on, it will turn more unstable with showers and longer spells of rain.”
Some reports had suggested temperatures could rise as high as 27C (80.6F) on Monday, but weather experts say a blast of warm air which is expected to hit Britain will bring lower temperatures than initially forecast.
The average maximum temperature for the UK in May is 14.7C (58.5C), while in England it is 16C (60.8F), according to the Met Office.
Forecaster Daniel Panton-King said: “There will be a fair amount of sun for most people.”
Last month saw the UK bask in the sunniest April on record, the Met Office said.
The country enjoyed an average 212 hours of sunshine, provisional figures showed, making it the sunniest April in records dating back to 1929 and beating the previous record set in April 1942 by seven hours.
The highest temperature of the year recorded so far was 25.1C (77.2F) in Faversham, Kent in April, MeteoGroup said.