Yes

you do need a jacket based on the weather in Montauk, NY 11954, USA 1 second ago

Why? Because it's cold. simple as that.
49°F10°C & Cloudy

Wind is 12 mph20 km/h from the E, gusting to 17 mph27 km/h
April 19
4pm49°F10°C12 mph20 km/h SECloudy
5pm49°F9°C12 mph19 km/h SEMostly Cloudy
6pm48°F9°C11 mph17 km/h SEMostly Cloudy
7pm47°F9°C11 mph18 km/h SEMostly Cloudy
8pm47°F8°C10 mph17 km/h SEMostly Cloudy
9pm47°F8°C10 mph15 km/h SECloudy
10pm47°F8°C9 mph14 km/h SECloudy
11pm46°F8°C8 mph12 km/h SCloudy
April 20
12am47°F8°C8 mph12 km/h SCloudy
1am47°F8°C7 mph11 km/h SCloudy
2am47°F8°C7 mph11 km/h SCloudy
3am47°F9°C8 mph13 km/h SCloudy
DateLowHighWindDayNight
April 1945°F7°C49°F10°C12 mph19 km/h from EMostly CloudyDrizzle
April 2047°F8°C53°F12°C8 mph12 km/h from SWRainWindy
April 2143°F6°C50°F10°C14 mph23 km/h from WMostly CloudyPartly Cloudy
April 2246°F8°C51°F11°C11 mph18 km/h from WClearClear
April 2343°F6°C50°F10°C13 mph21 km/h from SMostly ClearWindy
April 2447°F8°C54°F12°C21 mph33 km/h from SWWindyPartly Cloudy
April 2542°F6°C50°F10°C18 mph29 km/h from NWWindyWindy

Yes

Low of 46°F8°C, High of 53°F12°C
Wind: 8 mph12 km/h
Precipitation: 81% rain

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