In his speech, Powell said the US economy is in a "favourable place" and the Fed will "act as appropriate" to keep the economic expansion on track. Markets had been divided on what they thought Powell would say at the Jackson Hole, Wyoming, symposium, with some expecting him to announce a major stimulus measure while others believed he would downplay the chances of a September rate cut.
"It has been a positive trading week for the local currency thanks to global stimulus hopes and a slowdown in domestic inflation, which boost expectations of a (South African Reserve Bank) rate cut," Lukman Otunuga, a senior research analyst at FXTM, said in a note.
In equities, Johannesburg's broader All-share index fell 0.35% to 53,996 points, while the benchmark Top-40 index declined 0.39% to 48,248 points.
Retailers were among the biggest decliners, with Massmart shedding 7.81% to 40.26 rand, while Shoprite fell 3.61% to 116.29 rand.
In fixed income, the yield on the benchmark bond due in 2026 added 0.5 basis points to 8.275%.
Headline consumer price inflation slowed to 4.0% year-on-year in July, data from Statistics South Africa showed on Wednesday, the lowest since January and below a consensus forecast of 4.2%.