SYDNEY — French Open champion Jelena Ostapenko had an upset 7-6 (3), 6-1 loss to Ekaterina Makarova on a sweltering opening day of the Sydney International.

No. 3 Ostapenko was one of two highly-seeded players to exit the women’s draw in the first round, with fifth-seeded Kristina Mladenovic retiring earlier Sunday from her match while trailing Australian wildcard entry Ellen Perez 6-4, 4-2.

Elena Vesnina beat Lara Arruabarrena 6-2, 6-2 in a later match.

Julia Gorges also withdrew from the tournament Sunday after winning the ASB Classic final against Caroline Wozniacki in Auckland, New Zealand.

The conditions forced organizers to activate heat policies — including longer breaks between sets — during part of the day, with some areas of western Sydney experiencing the hottest day in almost 80 years with temperatures peaking above 47 Celsius (117 Fahrenheit).

In men’s first-round matches, Alexandr Dolgopolov edged Viktor Troicki 6-3, 6-7 (6), 7-5, Damir Dzumhur beat Jan-Lennard Struff 6-1, 6-4 and Paolo Lorenzi had a 7-6 (5), 6-4 win over Jordan Thompson.