After two days of dry conditions to start the tournament, a poor forecast proved correct as rain began to fall just before the scheduled start of play at 11am and quickly became steady.
Organisers immediately announced there would be no play before midday, but the forecast indicates the rain is not likely to clear before later this Tuesday afternoon.
The first round is due to be completed in the men's and women's singles today, with Elena Baltacha and Heather Watson scheduled third and fourth on Court Three, meaning there is a very good chance neither may play.
Rain is not uncommon at the French Open, and last year the men's final between Rafael Nadal and Novak Djokovic had to be completed on the third Monday.
The French Tennis Federation have announced plans to put a roof on the centre court, Philippe Chatrier, but it will be another five years at best before indoor play is possible.
The rain eased off enough for the courts to be uncovered shortly before 1.30pm, two and a half hours after play had been due to begin.
And the players then arrived on court despite steady drizzle continuing to fall.