Yes

you do need a jacket based on the weather in Johannesburg, South Africa 1 second ago

Why? Because it's not very warm out.
58°F14°C & Clear

Wind is 7 mph11 km/h from the N, gusting to 19 mph31 km/h
September 8
2am58°F15°C8 mph12 km/h NClear
3am63°F17°C10 mph16 km/h NWClear
4am68°F20°C12 mph19 km/h NWClear
5am72°F22°C13 mph21 km/h NWClear
6am75°F24°C13 mph21 km/h NWClear
7am76°F25°C13 mph21 km/h NWClear
8am78°F25°C12 mph19 km/h NWMostly Clear
9am78°F26°C12 mph19 km/h NWMostly Clear
10am77°F25°C11 mph18 km/h NWPartly Cloudy
11am76°F24°C10 mph17 km/h NWPartly Cloudy
12pm73°F23°C8 mph12 km/h NWMostly Clear
1pm70°F21°C6 mph10 km/h NWMostly Clear
DateLowHighWindDayNight
September 753°F11°C78°F26°C11 mph17 km/h from NWMostly ClearMostly Clear
September 852°F11°C78°F26°C10 mph15 km/h from NWMostly CloudyMostly Clear
September 946°F8°C71°F22°C13 mph21 km/h from NMostly ClearMostly Clear
September 1047°F9°C76°F25°C12 mph19 km/h from NMostly ClearClear
September 1157°F14°C81°F27°C12 mph19 km/h from NMostly ClearMostly Clear
September 1259°F15°C83°F29°C8 mph12 km/h from NMostly ClearMostly Clear
September 1361°F16°C85°F29°C11 mph18 km/h from NMostly ClearMostly Clear

Yes

Low of 52°F11°C, High of 78°F26°C
Wind: 10 mph15 km/h
Precipitation: None

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