Cesar said he struggled to keep warm during Tuesday's 2-1 win over North Korea on a freezing evening at Ellis Park.
"I was really cold," said Julio Cesar, who had almost nothing to do until the North Koreans scored their consolation goal in the 89th minute.
"You do your best, you use a special powder, but when you have nothing to do, it's very bad to play like that, especially in the cold.
"You have to try to keep warm and keep concentrating in case you're suddenly called upon to take part in the game."
Like several of his team mates, he also complained that the North Korean rank outsiders were too defensive in Tuesday's Group G match and made it difficult for Brazil to develop their normal game.
Widely considered the world's top player in his position, Julio Cesar said he hoped to avoid joining the growing list of goalkeepers who have blundered in the competition.
"I hope not to concede one of these goals," he said.
"It's an occupational hazard and when it happens in a World Cup, it is magnified and it can be ungratifying.
"But I'm well prepared and I hope in the next six games, I can play well and not make this type of mistake," he said, referring to the number of matches Brazil will play if they reach the final.
"A lot of goalkeepers are playing well, the Honduras goalkeeper (Noel Valladares) made a really outstanding save against Chile."
