Grand Prix fans are being warned not to attend the Silverstone race track on Saturday as heavy rain left thousands stranded in traffic jams near the site on Friday.
On Saturday morning, car passengers were being turned away, with persistent rain leaving many of the public car parks unusable.
More than 20,000 racing fans could be affected by the deluge.
The Silverstone switchboard warned: "It is with great regret that customers holding Saturday or weekend public car passes should not attempt to approach the circuit today as they will be turned away and could face heavy traffic.
"Please do not attempt to drive to Silverstone today without a ticket. We apologise for all inconvenience."
Silverstone managing director Richard Phillips issued an "unreserved apology" to fans, adding the incident almost reduced him to tears.
Phillips said the financial hit is likely to run into seven figures, which for this season will potentially turn a profit into a loss.
He said organisers were in emergency meetings every two hours with the police, highways agencies, county council, emergency planning to "try and resolve the issues."
He added: "It's going to cost us a lot of money. I honestly don't know the figure, but it could be a lot more than hundreds of thousands (of pounds).
"For people who did not get in we're offering refunds, and for anybody who doesn't get in we'll be offering refunds as well.
"Right now we're trying to get ourselves into a situation to get in as many people as we can from a position of devastation.
"But I unreservedly apologise to people. I feel very responsible for it, this is something I've been very proud of over the years and I almost could cry now."
Problems started when a deluge of up to 40 millimetres of rainfall fell in a 12-hour period.
By mid-afternoon all campsites in and around Silverstone had to be closed.
With camping grounds sodden, caravans and motorhomes had to be escorted in one at a time when ordinarily they would have driven straight in, backing up the traffic.
Crucially, it is the loss of the car parks that caused major headaches for all concerned as they hope for them to dry out to re-use them on Sunday.