Yes

you do need a jacket based on the weather in Port Kennedy WA 6172, Australia 1 second ago

Why? Because it's not very warm out.
53°F12°C & Clear

Wind is 10 mph16 km/h from the S, gusting to 15 mph24 km/h
September 20
11am53°F11°C10 mph16 km/h SClear
12pm52°F11°C10 mph16 km/h SClear
1pm50°F10°C9 mph15 km/h SEClear
2pm49°F10°C9 mph14 km/h SEClear
3pm48°F9°C8 mph14 km/h SEClear
4pm47°F9°C8 mph13 km/h SEClear
5pm47°F8°C7 mph12 km/h SEClear
6pm46°F8°C7 mph11 km/h SEClear
7pm48°F9°C7 mph12 km/h SEClear
8pm52°F11°C8 mph12 km/h SEClear
9pm57°F14°C8 mph14 km/h SEClear
10pm61°F16°C9 mph15 km/h SEClear
DateLowHighWindDayNight
September 1946°F8°C68°F20°C10 mph16 km/h from SClearClear
September 2046°F8°C69°F20°C11 mph17 km/h from SClearClear
September 2147°F8°C72°F22°C10 mph16 km/h from SClearClear
September 2250°F10°C68°F20°C14 mph22 km/h from SClearPartly Cloudy
September 2349°F9°C67°F19°C11 mph17 km/h from SPartly CloudyClear
September 2444°F6°C70°F21°C8 mph13 km/h from EMostly ClearPartly Cloudy
September 2553°F12°C74°F23°C10 mph17 km/h from NWMostly ClearPartly Cloudy

Yes

Low of 46°F8°C, High of 69°F21°C
Wind: 11 mph17 km/h
Precipitation: None

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