Thunderstorms could dampen performances from the likes of Craig David and Alicia Keys at the Platinum Party at the Palace on Saturday.
The Met Office is considering issuing a weather warning as it predicts heavy, possibly thundery, showers for parts of England and London on Saturday evening, during the Jubilee concert.
The forecaster is expected to review the situation on Friday morning.
Thunderstorms could hit the capital over the weekend
Dominic Lipinski
A total of 22,000 spectators are expected to attend the event outside Buckingham Palace.
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.
Mr Partridge said one of the main risks highlighted in a potential weather warning would be visibility on the roads and the impact on travel times for drivers.
He said: “I suppose it would be advice to take care or, at the very least, to leave extra time for journeys, because in those areas of rain, the visibility – because of the surface spray as well as just the rain on the road – will really mean you will have to reduce speeds.
“Certainly heavy rain with a risk of lightning and the usual associated risks there of some surface water issues, spray, poor visibility on the roads, and of course, if you are out, you are going to get wet.”
North-west England is also expected to see outbreaks of rain into Thursday night, possibly coinciding with the lighting of Jubilee beacons between 9pm and 10pm, before a generally warm and dry Friday.
Platinum Jubilee celebrations got underway today
Daniel Leal
As well as the risk of thunder, Saturday in England is likely to see some cloud and cooler temperatures of around 20C and 21C before moving into Sunday with lower temperatures of 18C and 19C, coupled with patchy outbreaks of rain.
Scotland is set to see its highest temperatures of the year on Sunday as cloud and showers make way for drier, brighter conditions over the weekend.
Mr Partridge said: “Sunday, Scotland will probably be the warmest place in the whole of the UK. We could very well see 23C to 24C down the west coast, which then would make that the warmest day of the year in Scotland so far.
“So if it does get too wet down in London then perhaps the Queen could go to Balmoral. It will be very nice, a fine end to the weekend there,” he added.
Scotland is forecast to have showers into Thursday night, turning heavy in some places with temperatures as low as 3C or 4C overnight before a bright and sunny day dotted with small showers on Friday and highs of 18C or 19C, and highs of 22C on Saturday.
Thursday brought highs of around 21C and 22C to Wales, with rain in places into the evening and Friday morning, before clearing up for sunny spells and patchy rain throughout the day with temperatures of 20C to 21C.
Wales will see a mostly dry Saturday but showers will inch their way into the southern parts of the country by the afternoon followed by a possibility of heavier, thundery showers into the evening with temperatures of around 18C.
Sunday is forecast to be much the same as England, with cooler temperatures, cloud, and showers that could turn heavy at times.
After a cool and showery Thursday, Northern Ireland will see an increasingly dry and bright Friday with temperatures reaching around 18C.
Saturday will bring more sunny, dry conditions and highs of 20C before cooling slightly to around 19C with some cloud returning into Sunday evening.