PARIS - Persistent rain accompanied by a flood warning washed out an entire day's play at the French Open on Monday for the first time since 2000, throwing an unwelcome spotlight on delayed plans to build a retractable roof over Centre Court.

Spectators leave after matches are cancelled due to rain.  [Photo/Agencies]

The abandonment also created a scheduling headache for organisers, who called off play shortly before 2pm local time, pushing 10 fourth round singles matches, including those featuring world number ones Novak Djokovic and Serena Williams, back to Tuesday.

While the three other grand slams - Wimbledon, US and Australian Opens - all have at least one showcourt with a roof, Roland Garros fans will have to wait till 2020 or later before any covering appears.

French Open director Guy Forget said Monday's non-event - coming on top of four rain-affected days earlier in the tournament - proved that installing a roof as soon as possible was essential.

Roland Garros's redevelopment plans have been put on hold by environmental activists looking to protect nearby greenhouses.

"For those in our country who still have doubts and who ask themselves 'do we absolutely need to modernise our stadium?', look at the facts. Today offers proof that this is absolutely necessary," Forget told reporters.

Monday's flood warning from the French national weather was at orange - the second highest alert level - and covered parts of northern France including Paris and surrounding areas, and said heavy rains could continue until Tuesday afternoon.

Instead of staging just four quarter-finals on Tuesday, organisers - who told soggy and disappointed fans to apply for refunds from the tournament's website - will have to clear the backlog of last-16 matches first.

Now only two men's quarter-finals will take place on Tuesday, defending champion Stan Wawrinka's showdown with Albert Ramos Vinolas and second seed Andy Murray's highly-anticipated duel with French favourite Richard Gasquet.

The delays will also affect competitors as those hoping to win the title will have to play matches on successive days if the tournament is to finish on Sunday as scheduled.

More than 50 first-round matches were held over during the previous washout on May 30, 2000. That tournament finished on time.

Rain forced the postponement of the 2012 men's final between Djokovic and Rafael Nadal, which was held over two days and finished on the Monday.

PONCHOS AND UMBRELLAS

While a handful of sodden spectators sat hunched under umbrellas on Court Philippe Chatrier on Monday watching a replay of Gasquet's emotional win over Japanese fifth seed Kei Nishikori a day earlier, thousands of others took shelter by cramming into the corridors under the main showcourts.

Americans Dot Hillegass and daughter Kim McGeorge had tickets for Chatrier - on what was to have been a highlight of a six-day trip to Europe and their first experience of live professional tennis.

Told the washout was the tournament's first since 2000, Kim McGeorge remained philosophical. "What are the odds on that? It was obviously not meant to be," she said.

"It's a disappointment. They need a retractable roof," said her mother, unwittingly tapping into the day's hot debate.

The miserable weather meant brisk trading for the shops and boutiques in the grounds.

And there were no prizes for guessing which products were flying off the shelves.

"Above all, it's the umbrellas and ponchos that are doing well," said Vincent Martinez, human resources coordinator for shops selling Roland Garros-branded merchandise.

"But people are going home earlier so in general we prefer sunny days."

Souvenirs in hand, an estimated 25,000 ticket-holders started trudging out of the grounds at 1:48 pm - with their only memory being that they went to Roland Garros on the day rain washed out play for the first time in 16 years.

Shopping should be part of a special experience for tennis fans, Martinez said, adding: "Today was also unforgettable, though perhaps not in the best way."