Feeder opened the Isle of Wight Festival to an empty field as bad weather cast a dark cloud over the outdoor event.
More than 50,000 people are travelling to the festival which is being headlined by Pearl Jam, Tom Petty and the Heartbreakers and Bruce Springsteen and The E Street Band.
But hundreds of revellers were forced to sleep in their cars on Thursday night after traffic became gridlocked when the Isle of Wight Festival site turned into a mudbath caused by heavy rains.
Because of the delays in opening the main arena on Friday, after a light fell down in high winds, first act Feeder started playing to an almost empty field. After their first song, as the crowds started running in, the lead singer said: "Hurry up, they're coming in."
Traffic queues on Thursday caused ferry companies to suspend their services and about 600 people were stranded on ferries on the Solent as the boats could not be disembarked because of traffic build-up on the island.
The problems started after heavy rain fell, water-logging the event car parks at Seaclose Park, Newport, meaning that they became churned up with mud as cars began to arrive. This led to the car parks becoming inaccessible and long queues forming, stretching back to the port towns of Ryde and Cowes.
Police led many of those waiting to Newport Football Club where they were given shelter overnight.
A festival spokeswoman said: "If you are on the mainland we are advising people not to travel by car.
"There is a ferry service for foot passengers and this will be the easiest route. We are sorry for any disruptions caused."
Entertainment started on Thursday night for those who had reached the site although the Big Top stage was evacuated at one stage because of heavy wind and rains although did reopen again for headliners Primal Scream.