CEFN Sidan’s Boxing Day Walrus Dip has been cancelled for the first time in 24 years.
The arctic conditions have led to the decision which was taken today due to health and safety.
All the beach car parks and significant sections of the park roads are compacted with ice.
The forecast is for the thaw to come in at the earliest on Boxing Day which will be too late for this event as 1,000 cars arriving within an hour could cause serious problems.
The RNLI and St John Ambulance also need to be present and have to have advance warning of attendance.
Carmarthenshire County Council’s parks manager Neil Perry said: “We obviously apologise for having to cancel the event.
“Health and safety has to be our priority and the decision has been taken based on the conditions at the park which could be dangerous if such a high volume of people arrived.”
Over the years, hundreds of people have found the ideal tonic for getting over Christmas by jumping in the sea at Cefn Sidan no matter how cold.
The event has developed into a popular spectator sport with thousands turning up to watch daring souls who crash into the sea dressed in anything from bikinis, fairy or Viking costumes and even as pantomime horses.
Every year throws up new surprises and people collect thousands of pounds for charities.
Carmarthenshire’s executive board member for leisure Cllr Clive Scourfield said: “We know this is very disappointing for the crowds of  people who take part, and for those who come to watch.
“It is a wonderful event but unfortunately we can’t take any risks with health and safety at the park.
“Hopefully conditions will be more favourable next year and the event will be back with a bang.”
A sign is being put up at the main entrance of the car park and messages on the park answer machine to help inform people of the cancellation.