There was a complete washout at Roland Garros yesterday for the first time in 16 years.
The tournament has been blighted by poor weather this year but there had been enough dry spells to keep things broadly on schedule.
That changed on Monday as rain delayed the start of play and, with the forecast poor for the rest of the day, organisers decided to cancel all play at 1.40pm local time.
Top seeds Novak Djokovic and Serena Williams had been due to play their fourth-round matches but will now have to try again today.
One day lost to rain is not a major headache, but the worry is the forecast is not good for much of the rest of the week.
Forget, whose first tournament in the job has been far from smooth sailing, said: “Tomorrow should be be better and I’m pretty sure we can play some matches.
“We knew it was going to be horrible today, and it was even worse than what we thought, that’s why we sent the players back early.
“We changed the programme, we’re not too far behind, there are still reasons for optimism. I think that in two days we will be on time.”
All the fourth-round matches in the bottom half of both draws were completed on Sunday apart from the ones between second seed Agnieszka Radwanska and Tsvetana Pironkova and former finalists Simona Halep and Sam Stosur.
But the top halves were due to play on Monday and are now at a significant disadvantage.
For the men playing best-of-five-set matches, playing two days in a row is far from ideal, but that is now the scenario facing the likes of Djokovic, David Ferrer, Tomas Berdych and Dominic Thiem.
The first two men’s quarter-finals are also on the schedule for today, with Andy Murray due to play Richard Gasquet and defending champion Stan Wawrinka taking on Albert Ramos-Vinolas.
The French Open is now the only grand slam without any covered courts, with the roof over Arthur Ashe Stadium in New York due to be operational for the first time at this year’s US Open.
The Australian Open has three covered courts while Centre Court at Wimbledon acquired a roof in 2009 and Court One will be covered from 2019.
Plans for the redevelopment of Roland Garros, including a roof over Court Philippe Chatrier, were first drawn up in 2011, having been mooted for a lot longer, but have become embroiled in a planning dispute.
Local residents and environmentalists have objected to plans to expand the cramped site into the neighbouring botanic gardens and the project is now not expected to be completed until 2020, with the roof the final part of the jigsaw.
Forget used the washout to push the case for planning permission, saying: “For those in our country who still have doubts, who say, ‘Is it absolutely necessary to modernise our stadium?’ Look at the facts.
“Today is proof, it shows us that this is absolutely necessary. We must have a roof. The other day I laughed about it, I said that things are sometimes a little slow in France, but now the day has come to say stop.”