hunderstorms could dampen performances from the likes of Craig David and Alicia Keys at the BBC’s Platinum Party at the Palace on Saturday.
The forecaster is expected to review the situation on Friday morning.
A total of 22,000 spectators are expected to attend the event outside Buckingham Palace, which is set to be broadcast live on BBC One, BBC iPlayer and BBC Radio 2.
Met Office meteorologist Simon Partridge said: “It’s being monitored but at the moment there’s not enough confidence to issue any warnings.
“But it’s one that’s going to be reviewed tomorrow morning as to whether or not we do require a thunderstorm warning, simply because of the number of people we’re expecting in the capital on Saturday night, so that’s one area of slight concern in terms of weather causing some issues for festivities.”
The show will see appearances from stars including Sir David Attenborough, Emma Raducanu, David Beckham and Stephen Fry, as well as a specially recorded performance from Sir Elton John.
Diana Ross is also scheduled to close the two-and-a-half hour show with her first UK live performance in 15 years.
Temperatures will hover between 15-18C in the capital throughout the day, according to the Met Office.
The weather agency said that a plume of warm air arriving from the continent will influence conditions in southern and central areas, bringing showers that could turn heavy and thundery.
Met Office Deputy Chief Meteorologist Rebekah Sherwin said: “There remains some uncertainty on how far north it will stretch but southern areas are likely to see a spell of showers on Saturday and Sunday, which could turn heavy and thundery at times.
“However, there will also be some breaks in the cloud even here, and northern areas are most likely to stay fine and dry.”
Monday is set to be cloudy, with further heavy and possibly thundery showers expected in London.