Serena Williams 'paranoid' over Australian Open heat

Serena Williams on Wednesday said the Australian Open heat was making her paranoid with the world number one waking up during the night to keep hydrated and avoid cramp.

The top seed played in 40 Celsius (104 Fahrenheit) conditions and said the thought of it kept her awake overnight after players fainted and vomited in the heat on Tuesday.

"It was definitely really hot today. I just tried to take it in my stride and do the best that I could," she said after cruising into the third round with a straight-sets win over Serbia's Vesna Dolonc.

Asked if she was doing anything special to prepare for the oven-like conditions, she said: "Just drinking a lot, making sure I stay hydrated.

"I kept waking up in the middle of the night last night, just paranoid. I just wanted to stay hydrated," she added.

"The last thing I want to do is to cramp in this weather. It can happen so easy. Just drinking a tremendous amount of water."

Nine players either retired or forfeited their matches on Tuesday in either heat or fitness-related incidents.

Croatia's Ivan Dodig became the latest casualty when he pulled out with cramp in the fourth set of his match against Damir Dzumhur on Wednesday.

"So far I have been okay," Williams added.

"I have been training for a long, long time in the heat in Florida as well as playing. I have been coming to Melbourne for years and years.

"So you just have to be ready for those hot conditions and just try to get through it."