Rafael Nadal: I feel sorry for Djokovic | Rafael Nadal: why I want to keep writing my blog | Murray's conqueror marches on | Family fortunes keep Verdasco on track | Serena Williams starting to feel the heat | GB's girls go from strength to strength | Russian women are weak in the mind | 'It wasn't better in my day', says Laver

Day or night, the next few days are forecast to feel as if one is permanently trapped in a steambath. There have not been four consecutive days of 40C (104F) temperatures in Victoria for 101 years, so if Andy Murray and Novak Djokovic - half of the Famous Four of the men's game - are upset that this Australian Open is no more for them, at least they are spared the prospect of roasting alive.

The consolation, albeit a minor one, for Roger Federer and Andy Roddick is that their semi-final is scheduled for 7.30pm tomorrow, by which time some of the sun's sting will have been drawn. Those in the line of fire on the first mercury-bubbling day are Fernando Verdasco, conqueror of Murray, and Jo-Wilfried Tsonga, last year's beaten finalist, whose quarter-final today will probably start about 3pm, when the court surface may be flammable. Rafael Nadal plays Gilles Simon in the evening session.

This championship relies on the Wet Bulb Globe Temperature (WBG), which measures the extent of heat and humidity. If it breaches a pre-determined threshold, Wayne McKewen, the referee, can suspend the start of matches on the outside courts. Then, and only then, he can also close the roof on the Rod Laver Arena and turn an outdoor event into an indoor one.

The most recent time that happened was on the opening day of the 2007 championships, when Maria Sharapova had completed her match against Camille Pin, of France, and the WBG exceeded safe limits.

Although Djokovic ground to a standstill in the fourth set of his quarter-final against Roddick yesterday, the heat was not considered a factor. “We had a sea breeze that picked up during the day and the temperature on court was just 25,” McKewen said. “At the airport [some 15 miles north], it was 35. Every decision we take is with the safety of everyone in mind, the ballkids and linespeople as much as the players. They are athletes who train for these conditions, but ballkids and linespeople don't. I take every decision in consultation with our chief medical officer. We are expecting very high temperatures in the next few days but almost no humidity to speak of.”

Yesterday, at two sets to one down and trailing 2-1, Djokovic retired, handing the match to Roddick, who, if he had not undergone a ferocious regimen over Christmas during which he lost a stone in weight, would have been unable to place the defending champion under the pressure that precipitated his capitulation in their quarter-final. “I had cramping and soreness in my whole body,” the 21-year-old Serb said. “I tried my best but you cannot fight your own body.”

Of more concern was the scheduling that meant that Djokovic completed his match against Marcos Baghdatis, of Cyprus, in the previous round at 2.26am, got to bed at 5.30, found sleep hard to come by, could not practise as he wanted later on Monday and was denied the evening start he asked for. That went to Federer, who wasted no time making mincemeat of Juan Martin Del Potro, from Argentina, 6-3, 6-0, 6-0. The world No 2 did not look as if he broke sweat. “This is not usual,” the Swiss said.

Federer has never quit a match; Djokovic has stopped four times - a statistic that the old pros haunting the corridors regard as the nearest thing to a misdemeanour - although there have always been mitigating circumstances. “There was absolutely no question about whether I had the motivation, the will and the desire to continue the match and defend my title,” Djokovic said. “My mind wanted me to carry on; I could have stopped in the second set because I felt really bad. I thought something could help me but the pain kept on coming back.”

Federer took an hour and 20 minutes to defeat the world No 6; Dinara Safina needed two hours and 19 minutes to put paid to Australia's remaining singles player, Jelena Dokic, 6-4, 4-6, 6-4. Dokic had not played in a grand-slam tournament for three years and was only a couple of better shot selections away from a semi-final. That turns up the heat on the credibility of the women's game.