Canadian qualifier Frank Dancevic collapsed during the second set of his first round match against Frenchman Benoit Paire and said he saw the comic character out on court as he suffered in the conditions.
He was unconscious for almost a minute but managed to return to the court before losing in straight sets.
"I was dizzy from the middle of the first set and then I saw Snoopy and I thought, 'Wow Snoopy, that's weird," Dancevic said.
"I couldn't keep my balance anymore and I leaned over the fence and when I woke up people were all around me."
Open officials said the temperature hit a high of 42.8 degrees at Melbourne Park as players and fans sweltered, with the heat expected to continue until the end of the week.
"It's inhumane and I don't think it's fair to anybody when you see players pulling out of matches and passing out," Dancevic said.
"It's hazardous to be out there, it's dangerous.
"Until somebody dies, they're going to keep playing playing matches in this heat ... and personally I don't think it's fair."
Dancevic said he questioned organisers about the heat policy before his match but was told it wasn't an issue.
"It's not only the heat you're battling with the air temperature, you're battling the heat coming from the court and also the sun so you've got heat coming from all sides.
Defending women's champion Victoria Azarenka described the conditions as like "dancing in a frying pan" .
Former women's world No.1 Caroline Wozniacki said when she put her water bottle down on court, the bottom started melting.
"It feels like I was sweating in a sauna or something," Wozniacki said.
China's Peng Shuai received a code violation after she vomited and cramped badly on court, blaming the heat for her three-set loss.
"I couldn't run, I couldn't serve so it was impossible for me to play," she said.
Daniel Gimeno-Traver helped a ball kid to his chair after he collapsed during the Spaniard's four-set loss to Milos Raonic while the St John Ambulance were kept busy treating fans for heat stress.
In 2009, the hottest edition on record with an average daily temperature of 34.7 degrees, reigning champion Novak Djokovic pulled out of his quarter-final with Andy Roddick, citing heat exhaustion.
Officials played down any health risks, pointing out that no player has ever died from dehydration on a tennis court.
Australian Open tournament referee Wayne McKewen said conditions were hot and uncomfortable but there was no need to invoke the extreme heat policy.
"The relatively low level of humidity ensured that conditions never deteriorated to a point where we needed to invoke the extreme heat policy," he said.
Dr Tim Wood, the Open's chief medical officer, said that the "playing group coped well".
"There were a few players who experienced heat related illness or discomfort but none required significant medical intervention after they had completed their match," he said.