Novak Djokovic and Serena Williams target quickfire second round wins at Wimbledon on Wednesday to escape the searing heat which will send temperatures soaring to a brutal 34 degrees. That would equal the record for the highest-ever temperature recorded at Wimbledon in 1976, the year when Bjorn Borg and Chris Evert were champions.

The heat rule will be introduced, allowing for a 10-minute break between the second and third sets of women's matches. However, the rule does not apply to the men's tour despite them having to slog it out over five sets.

Tennis: Wimbledon heat on Djokovic, Serena, SharapovaPeople in the queue to get into The All England Tennis Club fill water bottles on day three of the 2015 Wimbledon Championships in Wimbledon, southwest London, on July 1, 2015. Pic/PTI

Early Wednesday, All England Club chiefs closed the Centre Court roof to keep the 15,000-capacity arena air-conditioned. But it will be reopened for the start of play at 1200GMT as organisers insist on the integrity of the event as an outdoor grasscourt tournament.

"The Centre Court roof is currently closed to protect the playing surface from the heat. It will re-open at 11.30am. #Wimbledon," the tournament tweeted.

Defending champion Djokovic opens play on Centre Court against Finnish veteran Jarkko Niemenin. World number 92 Nieminen is playing in his 12th and last Wimbledon having ended the All England Club career of 2002 champion Lleyton Hewitt over five sets in the first round. Djokovic, also the 2011 champion, has a 5-1 career record over the 33-year-old Nieminen, a quarter-finalist in 2006. The last time Djokovic lost in the second round at a Grand Slam was at 2008 Wimbledon, when as number three seed he was defeated by Marat Safin.

Fourth seed and French Open champion Stan Wawrinka takes on world number 48 Victor Estrella Burgos, only the second Dominican Republic player to take part in a Grand Slam. Wawrinka recorded his best Wimbledon performance by reaching the quarter-finals in 2014.

Japanese fifth seed Kei Nishikori takes a 6-1 career lead into his second round match against Santiago Giraldo while 2014 semi-finalist Milos Raonic, the seventh seeded Canadian, faces German veteran Tommy Haas. At 37 years and 100 days old, Haas is bidding to become the oldest man to reach the third round at a Grand Slam since Jimmy Connors, who was just past his 39th birthday when he made the last 32 at the 1991 US Open.

US Open champion Marin Cilic, the ninth seed, meets Lithuania's Ricardas Berankis in a tussle between two former world junior number ones. Five-time women's champion and top seed Williams faces Hungary's Timea Babos as she continues her bid to sweep a calendar Grand Slam and a 21st major. Maria Sharapova, the 2004 champion and fourth seed, tackles Dutch qualifier Richel Hogenkamp.