Punters will be swapping sun cream for umbrellas at Worthy Farm as the weather is set to turn from “wall-to-wall sunshine” and high temperatures on Thursday morning to “heavy thundery downpours” in the afternoon.
The Met Office issued a yellow thunderstorm warning stretching from Sheffield in the North, across the South East and down to Bath in the South West, meaning Glastonbury revellers could be caught in torrential downpours in Somerset.
Meteorologist Sarah Kent, from the Met Office, told the PA news agency: “They are going to have a really warm night which is good news for people who are camping out there of course and a lovely start to the day, pretty much wall-to-wall sunshine.
“With that the heat will be gradually building through the morning and it’s that heat that could be part of the problem for the weather in the afternoon because we are looking at scattered showers coming in from the south.
“Those showers will be locally heavy and could be thundery, which is why we have a thunderstorm warning out from 10am all the way through to 11.59pm.”
The meteorologist said that the nature of thundery showers are that they are “hit and miss”.
She added: “We know they are going to occur, but whether they happen exactly in one particular point is extremely hard to get right even this far ahead so it’s a risk.
“If you did get a downpour tomorrow it is likely to be heavy and from blustery winds potentially tied in and the threat of some lightening as well – so it’s just to keep that in the festival-goers’ attention.
“They may need to take shelter if they can if one of those thunderstorms do come through in the afternoon.
“The warning area encapsulates the risk of those storms occurring anywhere within that area so it is not expected to get to Glastonbury until the afternoon but the caveat is it is difficult to get the exact distribution of showers, it is just the nature of showers this far ahead but we will be posting updates as they develop.”
Festival-goers have already been warned to pack for all eventualities – and take their wellies – at Glastonbury, with light showers predicted on Friday and Saturday, followed by more heavy rain on Sunday.
The weather warnings come as late arrivals battle more travel disruptions with another rail strike taking place on Thursday, likely adding to the transport issues revellers face with poor driving conditions and floodwater on roads.
Fewer than one in five trains ran on Tuesday after members of the Rail, Maritime and Transport union (RMT) on Network Rail (NR) and 13 train operators staged the first of three walkouts, with strikes set to follow on Thursday and Saturday.
Glastonbury is not the only music event set to be disrupted by the strikes this week, with The Rolling Stones performing at the British Summer Time festival in Hyde Park on Saturday and the Red Hot Chili Peppers due to take to the stage at the London Stadium on Sunday.
Beatles star Sir Paul McCartney will become the oldest ever solo headliner when he performs on Saturday at Glastonbury, a week after his 80th birthday, meanwhile this year will also play host to its youngest ever solo headliner in the form of 20-year-old Billie Eilish on Friday night.
Last minute changes to the line-up include rocker Terry Reid dropping out of his Sunday afternoon slot on the Acoustic Stage. He will be replaced by Glenn Tilbrook, lead singer and guitarist of Squeeze.