At 0733 GMT, the rand traded at 19.0775 against the dollar, about 0.5% weaker than its previous close.
U.S. Treasury yields hit 16-year highs on Wednesday, boosted by expectations that the Fed would keep interest rates higher for longer.
"If yields continue to rise, the USD will eventually run stronger," said Rand Merchant Bank analysts in a morning briefing.
The rand often takes its cues from global factors such as U.S. monetary policy in addition to local factors.
"The rate hike concerns and heightened Middle East tensions are driving the dollar stronger and dampening risk sentiment," said Andre Cilliers, currency strategist at TreasuryONE.
"Poor local retail sales data also did not help the rand's cause," Cilliers added.
Global markets will turn their attention to a speech by Powell later in the day for hints on the future interest rate path of the world's biggest economy.
Shares on the Johannesburg Stock Exchange opened lower, with the blue-chip Top-40 index down about 0.9%.
South Africa's benchmark 2030 government bond was weaker in early deals, with the yield up 13.5 basis points to 10.960%.
(Reporting by Tannur Anders; Editing by Bhargav Acharya and Alison Williams)
