At the 2026 Australian Open, top seed Jannik Sinner faced severe challenges due to extreme heat at Melbourne Park. Play was halted as the heat stress level reached five, prompting the roof to be closed. Sinner, the two-time defending champion, was visibly struggling with cramps, walking slowly between points, and receiving on-court treatment. Despite these conditions, Sinner managed to level the match after losing the first set 4-6 to American Eliot Spizzirri, who is ranked No.85. Spizzirri, a 24-year-old player from the University of Texas making his Grand Slam debut, played aggressively and was on the verge of an upset, with commentators noting that Sinner was 'in big trouble' and 'on the ropes.' Meanwhile, other matches saw top American players Keys and Pegula advancing comfortably, and Luciano Darderi defeated Karen Khachanov to reach the fourth round for the first time in a major. The tournament's heat scale reached 4.3, with temperatures approaching 37 degrees Celsius, leading to frequent breaks, hydration efforts, and ice vests for players. Sinner's condition remained precarious as he battled cramps, but he managed to win the second set 6-3, and the match continues amid the challenging conditions. The scheduling of the match in the hottest part of the day raised questions about player safety and tournament logistics.