Hundreds of revellers have been forced to sleep in their cars after traffic became gridlocked when the Isle of Wight Festival site turned into a mudbath caused by heavy rains.
The queues caused ferry companies to suspend their services and about 600 people were stranded last night 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 yesterday, 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.
Now organisers are urging anyone still waiting to get to the island to leave their cars.
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."
Promoter John Giddings said in an interview with BBC Radio Solent: "Believe you me, I am doing everything in my power and the police are telling me to do everything in my power, because they want an emergency plan from me by Sunday about how we are going to get people out."
Fiona Gregory, from Salehurst in East Sussex, said that she had left home at 1.30pm yesterday and was still stuck in queues in the early hours of this morning.
She told the BBC: "I'm so upset. It's a complete disaster. On the island it has been a nightmare. There is no police, no diversion signs, nothing.
"Now we're about two miles away on a country lane and we have moved one mile in the last four hours."
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.
Entertainment started last 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.
The Charlatans also played an exclusive warm-up gig at Spitbank Fort, a Napoleonic Fort in the middle of the Solent, organised by Absolute Radio.
A spokeswoman for Wightlink, which operates ferries from Portsmouth and Lymington to the island, said services had resumed as normal this morning.
She said: "Our ferries are currently running to schedule and on time."
Last night, members of Vectis 4x4 Response, a voluntary group which helps in emergencies, helped tow 358 vehicles to the car park.
John Marr, of Vectis 4x4, said: "We had eight vehicles on site. Even with a police escort to get us in, it took us an hour to get there.
"We moved 358 vehicles that were stuck in the mud. There is only one way into the car park and the conditions were the cause of all the hold-ups. We aren't to blame, but we did our best."
People have reported on social media sites how school buses have been stuck and cancelled because of the tailbacks, leading to pupils walking home in the rain yesterday.
Other people reportedly affected have been patients trying to reach hospital as well as those attending funerals at the crematorium close to the festival site.
A statement by Hampshire Police placed on Twitter said: "More car parks are open around the Seaclose Park site but IW Festival goers and residents are advised to still expect significant delays today.
"The festival's emergency liaison team is working closely together to explore other options to reduce traffic queues and minimise disruption as soon as possible.
"These options include opening other car parks across the island.
"Our priority is to clear existing traffic on the island and provide more welfare and refreshments to motorists in queues.
"Some motorists remain parked at Newport Football Club."
British Red Cross emergency teams have been helping campers at the festival deal with the extreme conditions.
They advised fans to ensure they are well prepared with the right clothing, food, equipment and contingency plans.
Donna Taylor, senior emergency response and planning officer, said: "Red Cross teams of staff and volunteers have been out responding to the disruptions caused by the wet weather at the festival.
"We deployed a team last night (Thursday June 21) to support emergency services and have been attending to first aid incidents helping the injured within the festival area itself.
"Our event first aid teams are on hand to assist people and are primarily based in the Strawberry Fields and Big Top area of the site, as well as being on foot patrol and on call to support other emergency services across the camp."
Traffic to the festival site eased this afternoon after cars were diverted to Robin Hill Country Park where a free bus service was laid on to take people to the festival site.
But access to the main stage area was delayed when high winds sparked safety concerns after a light apparently fell to the ground.
Because of the delays in opening the main arena, 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."