World No 4 Agnieszka Radwanska said it was "too hot to play tennis" and China's Li Na said it was like a sauna as the Sydney International was hit by a searing heatwave yesterday. Poland's Radwanska, who reached last year's Wimbledon final, battled fearsome temperatures topping 40 degrees Celsius to brush past Japanese veteran Kimiko Date-Krumm 6-4, 6-3. While Radwanska reached the last eight, the major talking point was not the standard of play but the blistering heat ahead of next week's first grand slam event of the year at the Australian Open in Melbourne. Li, who beat Japanese qualifier Ayumi Morita 6-1, 6-0, said she was reaching for the ice towels at each changeover. "I was feeling like playing in a sauna. At the first changeover I didn't use an ice towel. I was feeling the heat was coming and I was like: 'What's going on'? "At the next changeover I was like: 'OK, I need an ice towel every changeover, otherwise I don't know how to play on the court.' "It's too hot, but I'm still in the tournament, so it's good news." The temperature climbed to a high of 41.4 degrees in the early afternoon at the tournament, with cooler temperatures forecast for today. All the day's scheduled matches were completed despite the searing heat. "I think this is too hot to play tennis," Radwanska said. "Even for players, for ball kids, for the people sitting out there, I think it's just too hot." Radwanska said she was trying not to alter her game in the conditions, but admitted she had more of a battle with the heat than her opponent. German second seed Angelique Kerber overcame Kazakh qualifier Galina Voskoboeva 6-2, 7-5 - her opponent had to be treated for heat exhaustion - and said playing in Sydney would actually help next week. "I think it's a good preparation for Melbourne. Melbourne's weather can be the same," Kerber said. "So to have matches in this heat and also to just prepare before Melbourne." The Sydney tournament has an extreme heat policy but it only comes into effect at the discretion of the tournament referee. Tennis officials apply a complex formula factoring in heat, humidity, and wind to determine when on-court conditions become too stressful for the players.