The men’s singles semi-final on Friday between Carlos Alcaraz and Taylor Fritz was stopped twice in less than five minutes because of crowd emergencies, amid temperatures of 32C on Centre Court.
Wimbledon’s Centre Court roof is kept open by tournament organisers except in the event of rain or darkness.
Asked whether the roof should be closed after multiple crowd incidents, women’s singles finalist Iga Swiatek said: “I think it’s not possible for the tournament because I think the tournament is supposed to be outdoor tournament.
“From what I saw and heard on different tournaments, they’re usually not willing to close the roof when it’s not raining, when it’s not a necessity.
“I’m not sure why. Maybe there are some rules or something.”
The Polish player added: “On some courts when you close the roof, there is no air-conditioning any way.
“So here, I think they need air-conditioning to make the grass less humid.”
During the second set on Friday between defending men’s singles champion Alcaraz and Fritz, play was briefly stopped after a fan sitting in the sun at the front of a stand needed medical attention.
Chair umpire Marijana Veljovic could be heard saying “we’re just going to check if someone’s OK”, as a ball boy ran over with water to help the spectator.
Less than five minutes later, play was once again stopped, with Ms Veljovic saying: “We’re going to have to pause immediately. There’s somebody unwell.”
The second spectator, who was sitting in the sun behind the umpire’s chair, was covered with umbrellas while they received attention.
Three fans needed attention on Centre Court on Thursday in similarly hot conditions.
Temperatures are forecast to top 30C on Saturday for the women’s singles final.
Tennis world number one Aryna Sabalenka on Thursday handed water to spectators on Centre Court who needed help, as play was repeatedly stopped to deal with medical emergencies in the stands.
Tournament organisers have increased the number of communications reminding spectators to seek shade, drink plenty of water and take time out of the sun.
In its hot weather guidance, Wimbledon says that “guests are reminded to apply sunscreen regularly, and advised to wear light, breathable clothing, hats, caps and sunglasses”.
Fans were being handed out on Friday at Southfields tube station to spectators walking to the grounds in the morning sun.
Spectators on Henman Hill used electric fans to cool themselves down and umbrellas to avoid the sun, some sitting in shade at the base of the hill to avoid the heat.
Many Wimbledon staff did not wear jackets on Friday, and the tournament said shift patterns are “adjusted to limit heat exposure”.
Wimbledon previously said it had “significantly increased the number of Evian water refill stations year-on-year around the grounds”, with 6,700 reusable water bottles distributed to staff.
Organisers said they had also distributed more than 100 free water refill points around the grounds for general use.
During the first set of her semi-final against Amanda Anisimova on Thursday, Sabalenka handed a bottle of water and an ice pack into the stands to cheers on court.
Umbrellas were also passed into the stand to the supporter, and play was stopped while they received help.
Only a short time later, another spectator sitting in Centre Court’s east stand, which is open to the sun, needed attention, and Sabalenka once again walked across court to hand water into the crowd.
Many seats in the stand were subsequently left empty for periods of the match, as spectators left to seek shade.
In the next semi-final between Iga Swiatek and Belinda Bencic on Thursday, a third spectator on Centre Court needed medical assistance and was carried out on a stretcher.
Sabalenka, who was knocked out of the tournament by American Anisimova, said she hoped the spectators “feel better”, adding that the interruptions “did not interrupt the play” of her match.
Speaking at a press conference after the match, the Belarusian said: “I feel like London is not ready for this weather.
“It was super hot, and I can’t even imagine sitting in one place and the sun just constantly hitting you.”
Met Office spokesman Grahame Madge said: “Across the UK, heatwave conditions will remain in place until Sunday but, from then on, the heatwave will begin to break down with a return to cooler and more unsettled conditions.
“Temperatures in south-west London on Saturday are expected to reach 30C, possibly reaching 32C in some locations.
“On Sunday, high temperatures will remain, but absolute daytime highs are expected to be a little cooler compared with Saturday, with values reaching 29C, with a chance of some locations around the capital seeing 30C or above.”
The hottest opening day in Wimbledon’s history was recorded last week, with temperatures hitting 29.7C on Monday June 30 and rising to 34.2C on Tuesday July 1.
The men’s singles final on Sunday, with highs of 29C predicted, is unlikely to break the record of the warmest closing day on record of 34.1C recorded on July 3 1976.
Wimbledon has said the heat rule will apply for all singles events for players – which allows for a 10-minute break when the wet bulb globe temperature (WBGT) is at or above 30.1C.
The rule will apply after the second set for all best-of-three-set matches, and after the third for all best-of-five-set matches.
Players may leave the court during the break, but they may not receive coaching or medical treatment.
Former British tennis player Greg Rusedski said: “It was super, super hot the opening two days – when it’s hot, the ball goes through the air and it’s harder to control.
“That’s very untypical British weather and we’re going to get that again with the heatwave at the final weekend as well.”
The hottest day ever recorded during the Wimbledon fortnight was on July 1 2015, when temperatures soared to 35.7C, according to the Met Office.
The highest overnight minimum temperature was 20.8C recorded on June 27 1976 during a particularly warm summer.
The extreme heat during the 1976 tournament prompted organisers to allow umpires to remove their jackets.
