Yes

you do need a jacket based on the weather in Sydney NSW, Australia 36 seconds ago

Why? Because just cool enough for a jacket, but not warm enough to ditch it and there are strong winds blowing out there!
51°F10°C & Mostly Clear

Wind is 12 mph20 km/h from the West, gusting to 26 mph42 km/h
July 10
8am51°F10°C15 mph24 km/h WestClear
9am50°F10°C16 mph26 km/h WestWindy
10am50°F10°C16 mph25 km/h WestWindy
11am49°F10°C15 mph24 km/h WestClear
12pm49°F10°C15 mph24 km/h WestClear
1pm49°F9°C14 mph23 km/h WestClear
2pm49°F9°C13 mph21 km/h WestClear
3pm49°F9°C13 mph20 km/h WestClear
4pm49°F9°C11 mph18 km/h WestClear
5pm49°F9°C10 mph16 km/h WestClear
6pm49°F10°C9 mph14 km/h NorthwestClear
7pm52°F11°C9 mph15 km/h NorthwestClear
DateLowHighWindDayNight
July 950°F10°C60°F16°C15 mph24 km/h from NorthwestMostly ClearClear
July 1049°F9°C63°F17°C12 mph20 km/h from WestClearClear
July 1149°F9°C63°F17°C6 mph10 km/h from SouthwestClearMostly Clear
July 1244°F6°C64°F18°C6 mph9 km/h from NorthwestPartly CloudyMostly Clear
July 1348°F9°C62°F17°C7 mph11 km/h from SouthwestClearPartly Cloudy
July 1445°F7°C57°F14°C8 mph13 km/h from SouthwestDrizzleClear
July 1544°F6°C61°F16°C7 mph11 km/h from WestClearMostly Clear

Yes

Low of 49°F10°C, High of 64°F18°C
Wind: 12 mph20 km/h
Precipitation: None

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