Grace was two over par after three holes of his opening round before recovering to card a 69 and the world number 14 – the highest ranked player in the field - carried on where he left off.
The 27-year-old fired four birdies in a row from the second at Glendower Golf Club and bounced back from a bogey on the sixth by picking up further shots on the 10th and 11th shortly before play was suspended at 3pm local time.
No further play was possible, leaving Grace to share the lead with compatriot Keith Horne on eight under par as South African players occupied 11 of the top 13 places on the leaderboard.
Horne, who set the clubhouse target after adding a 69 to his opening 67, said: “I didn’t necessarily play as well as yesterday but the big thing was that I made no bogeys, which helps.
“I had some pretty poor chips and putts on the par fives; I parred all of them today which is frustrating because they are the scoring holes.”
England’s Ross McGowan was the best-placed non-South African, the world number 317 sharing fourth place on six under after a round of 70.