The speech was devoted mainly to the history of the ANC.
Many say the party hasn't delivered on its promises since taking power in 1994.
"We need to ensure that our programme of transforming our country is accelerated and taken to new heights," Zuma said, flanked by an aide holding an umbrella.
He acknowledged the problems confronting the ANC, saying it needs to "defeat the demon of factionalism" and to take "urgent and practical steps to restore the core values, stamp out factionalism and promote political discipline".
It is unclear if the ANC members who'd left the stadium during his address had gone because of the heat, because they had to leave due to lack of accommodation or whether they were sending Zuma a message.
One woman left saying she was bored.
Deputy President Kgalema Motlanthe proposed a toast and told the half-empty stadium that if they did not have champagne, they could take photographs of their leaders drinking, or raise clenched fists.
"The leaders will now enjoy the champagne, and of course they do so on your behalf through their lips," he said.