Lunch Australia 99 and 156 for 4 (Head 87*, Harmer 2-47) trail South Africa 425 for 9 dec by 170 runs
South Africa's bid to level the series in Gqeberha was frustrated by frequent squalls which blew over St George's Park on the final day, wiping out the opening session.
A couple of times play was close to starting only for the rain to return and covers to get pulled back into place. The forecast suggests that the weather will improve during the afternoon but Australia's hopes of salvaging a draw have been given a little helping hand.
The visitors crashed to 99 all out on the fourth day and were 156 for 4 in the follow-on, still 170 runs away from making South Africa bat again. Steven Smith has been forced down the order by a neck problem but will be able to bat on the final day. Australia's hopes of leaving with their series lead intact rest largely on him, Travis Head and Alex Carey.
"It's just a sore neck really," Josh Hazlewood said of Smith when speaking to Kayo Sports. "I think it's probably just from time in the middle and fielding in the slips, batting, training, all that sort of thing.
"Different pillows, or different beds, second night on tour doesn't help. I'm accustomed to a sore neck from time to time as well, so it's very annoying. In particular, when you're batting, it can be quite frustrating or quite debilitating. He looks better today, I think. He'll obviously bat at some stage, and he's the best in the world, so we need him."
There will be a runs and time equation for Australia when play does get underway because if they are able to wipe off the deficit, South Africa would have to chase a target for victory.
Marco Jansen did the major damage to Australia in their first innings with 5 for 33, while Simon Harmer has so far played a crucial role in the second, taking the wickets of Marnus Labuschagne and Beau Webster on the fourth evening as a howling gale blew across the ground.