But organizers of the Swiss festival, featuring the likes of British rocker Elton John (set to perform on Thursday night) and Belgian star Stromae (Wednesday night), say they are confident all is ready, noting that fair weather is forecast for most of the week.

“Except for cloudy and rainy front, everything looks good for this 39th edition,” president of the festival Daniel Rosselat, who is also Nyon mayor, told a press conference on Monday.

The festival was forced to implement its “rain plan” after precipitation of around 50 millimetres over two days.

Most of the parking area around the site of the festival will be closed because of the inundation.

Festivalgoers arriving in cars will be directed to park in the centre of Nyon where shuttle buses will transport people to the festival site north of the town centre.

A campsite for visitors to the six-day festival opened on Sunday in “mud and good spirits”, according to a blog on the festival’s website.

“We have a promise of nice weather for the rest of the week,” Rosselat said.

An estimated 230,000 spectators are expected at the festival, which runs until Sunday.

Other performers at the festival include James Blunt, the British singer-songwriter who has a home in nearby Verbier, The Prodigy, Placebo and The Black Keys, as well as French stars such as chansonnier Maxime LeForestier, Vanessa Paradis.

The festival has several stages and as in past years a “world village”, paying hommage this year to music from the Andes.

While the festival is largely sold out, 1,500 tickets will go on sale on the internet each morning, in addition to selected sales points (not on site).

For more information check the Paléo website.