Yes

you do need a jacket based on the weather in Mornington VIC 3931, Australia 1 second ago

Why? Because it's pretty chilly.
53°F12°C & Windy

Wind is 16 mph25 km/h from the NW, gusting to 25 mph41 km/h
September 21
11am53°F12°C16 mph26 km/h NWWindy
12pm53°F12°C16 mph25 km/h NWWindy
1pm52°F11°C16 mph25 km/h NWWindy
2pm52°F11°C16 mph26 km/h NWWindy
3pm52°F11°C16 mph25 km/h NWWindy
4pm52°F11°C16 mph25 km/h NWWindy
5pm52°F11°C16 mph25 km/h NWWindy
6pm54°F12°C16 mph26 km/h NWWindy
7pm55°F13°C16 mph26 km/h NWWindy
8pm57°F14°C16 mph26 km/h WWindy
9pm59°F15°C15 mph25 km/h WWindy
10pm60°F16°C15 mph25 km/h WWindy
DateLowHighWindDayNight
September 2152°F11°C62°F17°C14 mph22 km/h from WMostly CloudyMostly Clear
September 2252°F11°C62°F17°C12 mph19 km/h from NWMostly CloudyCloudy
September 2351°F11°C66°F19°C7 mph12 km/h from NCloudyRain
September 2447°F9°C56°F13°C12 mph20 km/h from SWRainPartly Cloudy
September 2546°F8°C55°F13°C10 mph16 km/h from SWMostly CloudyPartly Cloudy
September 2643°F6°C60°F16°C6 mph9 km/h from EMostly ClearMostly Clear
September 2745°F7°C66°F19°C8 mph12 km/h from NPartly CloudyMostly Cloudy

Yes

Low of 52°F11°C, High of 62°F17°C
Wind: 12 mph19 km/h
Precipitation: 18% rain

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