Welsh Rugby Union (WRU) officials say the Millennium Stadium roof was accidentally left open during heavy rain, leaving the pitch waterlogged and Friday's opponents Fiji unimpressed.

The sliding roof at the 75,000-capacity stadium was left open on Wednesday night and the rain that has flooded many parts of Wales has left the pitch saturated.

"We talked about the roof during the week, so we're quite surprised to see this," Fiji coach Wayne Pivac said as he ruefully surveyed the sodden turf.

"I guess they'll close it now, but it's not going to dry in time, is it? We would prefer it dry, but I guess it's the same for both sides."

A WRU spokeswoman tried to blame the Met Office for the gaffe.

"We were advised at 5pm on Wednesday that we wouldn't get any rain until 11am on Thursday, so we opened the roof," he said.

"We need to open the roof at times because the pitch needs a certain amount of air, light and water."

But a Met Office spokesman, who confirmed 5.8mm of rain fell in Cardiff overnight on Wednesday, said they had been predicting the downpour all week.

"We certainly weren't surprised by the amount of rain," he said. "We have been forecasting rain - and lots of it - all this week, and no-one here has told the Stadium otherwise.

"We don't have a contract with the WRU any more and we've had no contact with them."

Brought to you by AAP © 2024 AAP