Music fans at the Glastonbury Festival were hit by lightning and torrential rain on Friday morning, threatening to turn the event into a wash-out.
The BBC's Ian Youngs says the weather for the Somerset site turned "from scorching to soaking overnight".
The last of the 112,500 revellers are arriving to see top acts for the first day including the White Stripes, Doves and The Killers.
Weather forecasters say more rain is expected and may waterlog the site.
The heavy rain threatens to turn campsites into bogs. The ground is already becoming heavily waterlogged and muddy.
But festival organiser Michael Eavis said he was keeping his fingers crossed that there would be no repeat of the infamous "mudfest" of 1997.
He said: "It's different from 1997 when the site was very muddy. We've had four or five days of good weather so the ground is firm.
"We've also spent a lot of money on the drainage, so the main site should be OK."
Conditions are expected to brighten up at Mr Eavis' Worthy Farm, near Pilton, later on Friday.
Most of the crowd have already been on the site for one or two nights and have been enjoying the party atmosphere.
QUOTE BY BBC REPORTER "I just wish I had not left my wellies in my car"