Carl Yapp's show diary In pictures: First day pictures

Police said car parks at Llanelwedd in Powys were full on Monday, although organisers said some were open.

Organisers said they were just about coping with the traffic problems.

Heavy rain has also been a problem for several days, but show secretary Barry Jones said a �350,000 drainage scheme had significantly reduced the impact.

Mr Jones said progress with parking was slow and "not without difficulty".

"We are assessing the situation from hour to hour," he said.

The rain has been extreme, but our drainage system is in place and it's probably too strong to say it's saved the show, but it's helped significantly Royal Welsh Show secretary Barry Jones

"One car park is full, but my understanding is that others are open. We are looking at the possibility of opening up other car parking areas."

Cars overheating in the traffic jams was adding to the problems.

Last week, chief executive David Walters had to deny rumours that the event would not take place because of the rain.

Contingencies

Mr Walters said there was "absolutely no truth whatsoever" in the claims and described them as "irresponsible" and "malicious".

Mr Jones admitted the weather had been an issue.

"The rain has been quite heavy over the last few days and we can't be complacent," he added.

"Plans are to go ahead as normal, but there will have to be contingencies for some car parks.

Brollies to the fore as crowds - and rain - pour into the showground

"Visitors are advised to follow the signs and guidance from our stewards and the police along the route into the showground.

"The rain has been extreme, but our drainage system is in place and it's probably too strong to say it's saved the show, but it's helped significantly."

In an attempt to ease people's concerns about the weather, Mr Walters has said that "facilities are such that we can cope with virtually anything the weather has to offer".

Meanwhile, there are more than 7,600 animal entries this year, an increase of 209 on 2006.

Horse and pony entries account for nearly half the increase - up from 3,364 to 3,468 - mainly through larger numbers of Welsh mountain ponies.

More than 240,000 people attended last year's Royal Welsh, one of the largest events of its type in Europe.