At 1540 GMT, the rand traded at 18.5750 against the dollar, down 1.6% on its previous close.
The dollar was up 0.7% at 102.13 against a basket of global currencies, on track for its biggest daily percentage gain since October.
With no major domestic economic data releases due till Thursday, the rand is expected to take its cues from offshore drivers.
The global market focus this week is on economic data that could shed more light on the trajectory for U.S. interest rates.
Minutes from the last U.S. Federal Reserve meeting in December are scheduled for release on Thursday and will provide insight into the central bankers' thinking around rate cuts this year. There will also be a U.S. jobs report on Friday.
In South Africa, a whole-economy purchasing managers' index survey is due to be published on Thursday.
On the Johannesburg Stock Exchange, the Top-40 index closed over 1.6% lower. The benchmark 2030 government bond was weaker, with the yield up 8.5 basis points to 9.855%.
(Reporting by Alexander Winning and Bhargav Acharya; Editing by Andrew Heavens and Ed Osmond)
