Climate change is leading to increasingly severe and recurrent weather events, which also cause...
kicking his heels in the locker room as torrential rain swamped Roland Garros.
The world number one then had the unexpected bonus of seeing potential quarter-final dangerman Richard Gasquet pull out of the tournament because of a knee injury.
Top seed Federer, still missing a Roland Garros title from his collection of 12 Grand Slam trophies, saw off America's world number 40 Sam Querrey 6-4, 6-4, 6-3 and will now face either Spain's Albert Montanes or close friend Kristof Vliegen of Belgium for a place in the last 32.
"This was a potentially dangerous match so I'm happy to get through," said Federer whose run-up to Roland Garros featured defeats against Nadal in the Monte Carlo and Hamburg finals.
"I've played well all claycourt season long. Now it's just a matter of getting used to the conditions."
Frustratingly for Nadal, the heavy rain, which eventually allowed just 26 of the day's scheduled 58 matches to be completed, arrived just as he was preparing to come on court to tackle Brazilian qualifier Thomaz Bellucci.
Nadal is hoping to make history by joining Bjorn Borg as the only four-in-a-row winner of the men's title.
The second seeded Spaniard comes into Roland Garros boasting a perfect record of 21 wins in 21 matches here and an intimidating run of 108 wins in 110 claycourt outings since April 2005.
He has also defeated Federer in the last two finals.
Gasquet's injury was another devastating blow to home hopes, 25 years after Yannick Noah delivered the country's last men's title.
The 25-year-old's decision to quit just hours before he was due to face compatriot Florent Serra in the first round follows Australian Open runner-up Jo-Wilfried Tsonga's withdrawal at the weekend also because of a knee injury.
"It's unfortunate," said world eighth-seeded Gasquet.
"After Saturday's practice session my knee was aching. It's been like that for the past two days.
"But I'm not going to dwell on my fate. I'm extremely disappointed I can't play here but I'll concentrate on Wimbledon."
Cypriot Marcos Baghdatis, the 17th seed who spent his formative years in Paris, was knocked out 6-2, 6-4, 6-2 by Italy's Simone Bolelli who goes on to face Argentina's Juan Martin del Potro.
Guillermo Coria, the 2004 runner-up who is slowly trying to rebuild his career after a year on the sidelines because of a shoulder injury, gave Spanish 12th seed Tommy Robredo a scare when he took the first set.
But Robredo, three times a quarter-finalist, eventually wrapped up a 5-7, 6-4, 6-1, 6-4 win and will next face either Serbia's Victor Troiki or Marc Gicquel of France.
Coria's fellow Argentine Guillermo Canas, the 29th seed, was also beaten losing 7-6 (8/6), 7-6 (7/5), 7-6 (10/8) to American wildcard Wayne Odesnik.
In the women's event, Serbian third seed Jelena Jankovic, who reached the semi-finals last year, enjoyed a 7-6 (7/3), 6-2 victory over Romanian lucky loser Monica Niculescu.
The 23-year-old will next meet either Italy's Tathiana Garbin or New Zealander Marina Erakovic as she plans to make the most of the shock retirement of Justine Henin, the winner here for the last three years.
"I don't see myself as the favourite," said Jankovic. "I am the number three in the world. There are others who are favourites but I feel I have made improvements.
"I have played in three Grand Slam semi-finals and lost to the eventual winner. Justine was the one against whom I always had the most trouble, so I have a better chance now."
American eighth seed Venus Williams, runner-up to sister Serena in 2002, kicked off her 12th consecutive Roland Garros with a hard-fought 6-3, 4-6, 6-2 win over Israel's Tzipora Obziler, at 35 the oldest player in the draw.
Williams now faces Tunisia's Selima Sfar for a place in the last 32.
Read moreAll news
In Frankurt, Germany, Doors Open is part of Dream Up, the international programme of the BNP...
The final of the Fed Cup by BNP Paribas 2019 tournament took place on the 9 and 10 November in...